As always, these are just my personal musings and don't represent anything design related, especially in regards to D&D Next (though that is the focus of my Musings).
I have a confession to make: 3.5 is my favorite edition when it comes to monsters. Yes, 4th edition critters are easier to use at the table, but I much prefer the 3.5 way of designing monsters. Here's why - I like completely wacky character options. I want to play a half-celestial unicorn paladin. I want to play a troll barbarian. 3.5 monsters are designed pretty much the same way player characters are so I can grab any given monster and make a character out of it.
I know I can just reflavor but, and here's another confession, I really don't like reflavoring. Well, I do, but within certain limits. Point, and I do have one, is that I'd rather have a critter that "feels" like a troll, both mechanically and flavorfully.
So, what's all this have to do with D&D Next? I'd like to see a mix of 3.5 and 4E when it comes to monster design. I'd like most humanoid monsters (and even a few non-humanoids) to have a little blurb of PC stats that distill the essence of the critter down to something I can play from level one (I do admit that 3.5's level adjustment mechanic was...painful, at times). I'd also like to see a little blurb on appropriate monsters being companion critters. Dire animals, unicorns, hippogriffs, even dragons...anything that could be used as a mount or other type of companion.
The ultimate point in all this rambling about monsters is that I'd like to see the Monster Manual for D&D Next be as much a player resource as a DM resource...because, let's face it, players are going to read it anyway.