Drop Gamespy - no way, GameSpy provided master servers for all of the Unreal series games to date. If they completely dropped it, they would basically drop UT2004, UT2003, UT99, U1... But making it less relying on that would be a good choice - leave only the MS of GameSpy.
Improve Netcode - 100% agreed, all I see on the demo in the Ping tab is 9999.
Add announcer voices - maybe, but I don't think it's a primary concern.
redo UI/GUI - 100% agreed again, that blood theme and FPS drain in the menu is awful.
remove dorky looking creatures on the startup splash screen of UT3 - Not a primary concern again.
no more inflated space shoes with leather belts - I can't say I liked holographic shields too much. Though they could make it the Unreal II style - different armour costumes that you can charge by killing enemies or taking pickups...
add a spectator tab - agreed again.
built in IRC chat client - yeap, they had it from UT99 as well, why didn't they add it here?
And you forgot some other main points:
Make the installer more friendly - that is, make sure people CAN install the game without the need of using workarounds.
Optimise the performance - make it give you more FPS (if possible), and add not some kind of a simple scroller to adjust the quality, but make it as selectable as in UT2004 - 10 tabs with full settings and descriptions.
Reduce load time - it takes me like 5 minutes to actually load the game, WTF?! UT2004 starts in a few seconds!
And now I don't play UT3 mainly for performance issues. And if I decrease everything to the minimum, it looks a lot worse than UT2004. So I do get why many people don't play it. Quote from Reaper's knowledge:
It looks like a ****, performs like a ****.... It's a ****.