I feel like I've never played Dwarf Fortress before with this new version even though I've built several forts in the old version. So much has changed, it's like re-learning the whole thing.
Without the wiki close at-hand this game seems all but impossible to figure out what to do. Besides all the new options, items, and structures to be built, the new z-axis alone exponentially increases the difficulty of playing. My first few times through I just felt completely overwhelmed because my Dwarves were getting their butts handed to them by repeated monster attacks.
In the old version I was able to last at least through a couple seasons. Now I can barely get through spring time before I've lost my fortress. Now think of what happens to a brand-new player coming into this version. I heard a few people complaining about how easy it has become since you can now bring along a lot more stuff, but I think this helps counterbalance the difficulty a little bit.
Until all the game mechanics can be re-written in the wiki, I think I'll have a hard time with this. I don't think it's quite right that I need to study a wiki anyway, before I can even play Fortress Mode.
I don't know what you think, but after the bugs die down in this release, the next step ought to be a complete interface overhaul. Sure, the keys and functions will change, but I think the whole thing needs a new, cleaner framework with mouse support and context-sensitive menus. The new z-axis poses so many problems to the current key system. I really believe that a new system can be designed without railroading future updates.