I haven't played online yet, so I don't quite yet know what to think about gameplay. The botmatches was pretty enjoyable, though I'm rather bored of vanilla UT now. Jumps feel less "floaty", which I'm not sure what to think about yet. The Dark-Walker is fun as hell, though kind of weird on a DM match. Goliath also handles much better than in UT2004.
I also really like the knockback and "Feign Death" features. Basically you get turned into a ragdoll and get up from where-ever you landed. I can't wait to see that in a Melee gametype (if we ever get one

The GUI is rather poor. There's sliders for mouse sensitivity, with only integer values, so no fine-tuning your mouse sensitivity there. There's a real lack of graphical customization options as well, with only 3 sliders for the Advanced video options (Texture, World Detail, and "Screen Percentage"). There's also this annoying habit of prompting you if you want to start the game when you click the "start" button, which you can't disable.
The HUD is pretty blah as well. It doesn't convey information as well as UT2004's did, is rather ugly overall.
I'm also not a huge fan of the graphics. Sure it's pretty, but the excess of bloom effects make it rather hard to see. It feels like my character's myopic or something. The excessively art style is also just way too gritty. There doesn't seem to be anything smooth in this game at all, which Is rather weird. Not a lot of color contrast either. Everything seems washed-out, and the only vivid colors you see are from neon lights and weapon effects. I miss UT2004's color and general art direction.
Of course, I am running this on a laptop with a fairly low-end card, so I guess I can't really judge graphics until I can play it on higher settings.
What does everyone else think?