I don't feel like classifying this version in terms of good/bad, whatever. It feels more like a preview of DF 2012 to me. With worldgen being dramatically slower the longer it runs, with certain sites in adv mode being unplayable laggy (capitol cities in longer world-gens), and most of all save-game failure or corruption being rampant both on save, retire, abandon, and crumble.. It's like you can play for a bit, get a taste of the new features, but you shouldn't get attached.
I do like a lot of the new features, don't get me wrong, but I'm happiest with it if I consider it like a demonstration of new features and not a version that I'm going to do anything much with. Really looking forward to a fix for the major crashes and save corruption, then I'll really get into it.
I genned 125 years and haven't had a single crash or bug, aside from the harmless book duplicating thing.
The good:
Everything. I love every new change to adventure mode. Necro powers are gloriously overpowered and immensely fun. Ranged weapons are fun again.
The bad:
Lack of large garrisons to defeat. Having 50 zombie pets isn't as fun as it can be. Throwing (at least with bolts/arrows) is still overpowered and is more powerful than ranged weapons due to lack of a reload time.
The ugly:
A mid week release means I am not doing as much work as I should be.

This version isn't ever going to get old.