I'm kinda with 'thatguyyaknow' here. The complexity limit and stats system kind of seems like it would make a lot of the parts less used than others. Without seeing the other parts it makes me wonder if any of the earlier, less expensive parts will be useful at all late-game. Depends on the bonuses they provide, I guess.
The animations have gotten a lot more rigid. It seems worrying about center of mass is gone - the big-headed tweety example Will showed would be just as fast as any other with the same parts. That and it doesn't matter what limb configuration you come up with - the max speed appears to be 5, and feet (?) appear to matter more than limbs. The legs will go at a blur if they're small and your creature has a lot of them, and when you have longer ones, it just looks silly. It just isn't nearly as impressive a simulation as it was before. It's still damn cool, but some of the magic is gone.
I think the complexity limit is there to limit file size and system requirements more than for balance. There's already a hard limit on the maximum amount you can have in an ability, and anyway, it's a single player game, why not let players get extremely powerful creatures if they want? Since the assets are made by other players, you can always stick in a nastier predator if you need one, although I suppose there has to be a limit.
One fear I had confirmed by this is that there's very little detail as far as the creature forms go. You can make a blob and stick things on it, and some of them have the dimension modifiers you want, some of them don't. Most of them don't scale as far as they really should be able to. You can't shape the blob beyond expanding and contracting around the spine - there's no surface deformation, etc, which should be possible given that it uses Maya. It's just very clutzy, probably so that people don't get confused, but it'd be nice to have more advanced features if you wanted them. You also can't put things on a lot of the other parts - as far as I can recall it's limited to feet, hands, limbs, and mouths.
As far as visual creativity goes, it's great, but if you wanted a creature that couldn't sneak to use the whip-like things, for instance (very attractive part, IMO), you're out of luck. It'd be really nice if you could add on parts without cost or benefit, just for aesthetics - nature is full of iterative processes, and it doesn't make sense that it costs the same to add an additional feather if you already have four.
I would absolutely love this if they could make a more detailed editor. Even if you couldn't download creatures from their servers, and had to manually download them yourself so that things didn't get too clogged, the complexity limit irked the hell out of me, and it's only going to get more irritating in the building/vehicle editors.