Wow, I wish I had kept up with this thread more
New release has a lot of cool features, but is pretty buggy at the moment. Dwarves that perform surgery, much more detailed combat (and cooler injuries that can result), better army management, a few tools to macro-manage your dwarves... and, among the bugs, rain that boils when it hits any living thing and (probably) kills them.
If anyone's looking to get into it now, I'd hold off for a few months until a less-buggy version is out.