It is obvious that this early playtest failed to learn any of the important lessons of the last 15 years of game design, or what was good and bad about 4th edition.
Good things that were forgotten:
1) All the rules are on your character sheet. The fact that, in 4th edition, your powers were all on power cards attached to your character sheet made the game infinitely better. Anything which steps away from this is a terrible, terrible idea from a usability standpoint. As such, spell memorization (as per the way the new wizard works) is, simply put, a bad idea. It adds confusion and slows down gameplay greatly as the caster has to sit down and figure out what spells to memorize. Having a set power list makes the game infinitely more accessible, and causes much less slowdown - every time you have to open up the rulebooks to figure out how something works is an indication you've done something wrong.
2) The attacker always rolls. Saving throws (rolled by the defender) as opposed to attack rolls (rolled by the attacker) are always always always a bad idea. Why? Because it breaks convention. The character attempting an action should always make the roll; this makes the game behave in a much more uniform manner and prevents people from getting confused and makes people have to wait less on other people rolling. If a monster casts a fireball on the characters, and everyone has to roll a saving throw, it is a lot slower than if the monster just throws five dice, one for each character.
3) Everyone uses the same basic set of rules. If you have spellcasters basically use an entirely different set of rules from nonspellcasters, the game is going to suck. Period. It will inevitably lead to imbalance and greater complexity, and both are bad. You want characters to work consistently from class to class. Don't have spellcasters have spells and non-spellcasters lack them, then non-spellcasters are boring (and probably weaker).
4) Everyone is always useful. A wizard should always be able to cast useful spells, and should not be forced to pick between being useful in combat and being useful out of combat; the same applies to every single character class. Putting combat and noncombat powers together is always a mistake.
5) People in heavy armor having as high or higher armor class than people in light armor. It is good for everyone's AC to be close together, but the current design basically says that you should only wear light or heavy armor (the middle armors can never be better than light armor, they can only be worse than it unless your dexterity modifier is 0 - in which case you should be wearing heavy armor). The current system will almost invariably make the highly dexterous thief harder to hit than the warrior carrying a two-handed weapon, and the thief sacrificed nothing for their high AC.
6) Combat and noncombat options need to be separated. 4th edition did a decent job of this (a few utility powers failed here, though), but it looks like from the playtest document that damage dealing spells and spells that are not used in combat are occupying the same spots. This is just bad design in a game as combat centric as D&D is. Noncombat options need to be kept seperate, and no class should have a monopoly over them - and you need to make sure that fighters have as many noncombat options as rogues and wizards do.
Lessons that weren't learned:
1) Complexity is bad. D&D is complicated, and every edition since at least 2nd edition AD&D has been more complicated than the previous one. 3rd edition was much more complicated than second edition was and, thanks to the much faster leveling, more players encountered more complexity, resulting in an enormous mess as 3rd edition, like those before it, had little real numerical basis underlining it. 4th edition fixed the problems of 3rd edition, but it was even more complicated than 3rd edition in many ways - while there wasn't as much bad complexity in the way of high level Vancian casters, a high level 4th edition character had a huge number of -meaningful- choices at any given moment, which could be intimidating. This is such a big issue that I'm going to break out each of the places where it is a problem.
2) Character creation is too complicated. Characters have too many build options for most reasonable people to consider, and the huge number of options lead to a large number of subpar trap options along with a small number of good options, and the more options came out, the harder it was to separate the chaff from the wheat.
3) Feats, in particular, are an enormous failure - 3rd edition introduced them and 4th edition continued them, but in both cases, in my experience, they were the major sticking point for both new and veteran players. There are far too many feats, and the shared feat pool leads to all sorts of nonsense, not to mention dangerous combinations and just plain old analysis paralysis while making or levelling characters. Lessening customization options will, rather oddly, actually make making and levelling characters a more enjoyable, less intimiating, and less onerous experience.
4) Characters have too many options while playing them. High level casters have always had this issue, but 4th edition made it so that everyone had a lot of meaningful options. While this SOUNDS fun, in practice it often lead to analysis paralysis amongst many players, where they were unable to choose between their options and they considered what to do for far too long. It disrupted combat and kept it from flowing smoothly. All characters (and this includes casters - in fact, I will go so far as to say it ESPECIALLY includes casters) need far fewer options, or perhaps, more accurately, far fewer rules-based options.
5) Characters have too many magical items. This is yet another example of something that seemed good not working out. In 2nd edition, magical items were rare and valuable; they were seen as special. In 3rd edition they were commoditized and every character had a full set of equipment like a Diablo character. This seemed like a good idea at the time but in practice it made magical items much less special, and yet another thing to keep track of; this was carried over into 4th edition. D&D is not Diablo; the current rate of magic item dispensation doesn't work right, magic items don't feel special, and magic items that actually do interesting things only further add to the complexity of characters. While this wasn't really explicitly covered in the playtest document, I'm pretty sure this is going to be perpetuated. This is bad. Adding further complexity to already overcomplicated characters is bad, and ultimately the straight up numerical bonus items are rather boring and feel like a given. A better model is for characters to have far fewer magical items, but any magical item they get is actually significant.
6) Classes need to be of equal complexity. 4th edition actually did a very good job of this; all the classes are about equally difficult to play and understand, and while the overall complexity level of the game is a bit high, the complexity balance BETWEEN classes was actually quite reasonable.
7) Powers are good. While the format of the power cards could potentially be improved, the overall idea of them worked pretty well, and the game needs to be designed so that it works this way.
8) Characters need to have more options than "I attack". There is no reason why a fighter should have fewer combat options than a wizard does, and it has a significant funness impact on both classes, as well as presenting significant balance issues.
9) Needless rolling for healing out of combat. This is just obnoxious and a waste of time and brainspace. Let characters heal a set amount of hit points, rather than forcing them to roll. Honestly, I'm not sure whether the whole "daily healing amount" is even the correct approach - it might be better to try and limit it in some other way, or just not care and start characters at full hp every combat unless circumstances dictate otherwise.
These rules are not ready to be put out into the wild and playtested. There was a fundamental misapproach to the game in the first place.
If you want D&D Next to be successful, here is what you need to do: You need to make the game simple enough that a 13 year old kid who has heard about D&D from TV/the internet can just pick up the books at Barnes and Nobles and play the game with his friends, without any external help or encouragement from anyone who played the game before. This needs to be the exact same version of the game that everyone else in the universe plays, not some dumbed down version of the game - the game should be that simple. And if someone else gives them the book so that they can join their playgroup, that book should be enough for them to play, without instruction.