I played 5e at D&DXP and I loved it. Without breaking the NDA let me explain why I liked it.
First I will describe my background and what I liked and disliked about various editions.
I like all editions of D&D. None are perfect but all have their good and bad points. Most of my experience with D&D is 1e and 4e with a little basic and 3.5 thrown in. I have never played OD&D, 3e, or 2e (but am somewhat familiar with them).
I like the earlier editions for their simplicity. Running a combat encounter as a DM with only very occasional glances at the monster stats is very refreshing. I liked that magic items were difficult and time consuming to create.
From the earlier editions I don’t like the lack of a general skill system. I also didn’t like how weak magic-users/wizards began or how powerful they got compared to other characters (although we didn’t play much higher level stuff so this wasn’t that much of an issue). Also, despite the general simplicity it did have some convoluted rules (more 1e than basic – basic was much cleaner).
In 4e I like that there is a general skills system. I like that each class has multiple built-in combat options. I like the generally pretty simple combat rules. I like the balance of the classes at each level (but I would be willing to give up “some” balance to other things I like – but I don’t want to throw balance out the window altogether). I love healing surges.
What I don’t like about 4e is the simple combat rules get convoluted by things like marking and interrupts. I think there are too many options in 4e. I don’t like easily made magic items. I don’t like that things that once were special (e.g. magic items and planar travel) became mundane. I hate most of the in-combat healing. I hate that a great concept like minions was devalued by things like at-will AoE attacks.
I sum up 4e I like to say I love the direction it took the game, but I think they just went too far with it.
Back to 5e, why do I like what I have seen? I saw much of my likes of 1e and 4e in some form in the playtest or have heard the developers discussing that they will be there, and much of my dislikes of both editions were not there or were very toned down.