I'll update/edit this post as I find stuff.
Wherever it says [fixed], that means it's fixed on my specific system by whatever I put as my fix, it does not mean it's fixed in the distro itself. This is purely my findings as a private citizen I have nothing to do with UU in any official capacity:
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1. Kubuntu docs causes some kind of script error whenever you add packages. Uninstalling kubuntu-docs fixes it. [fixed]
2. The default home-page link in Firefox doesn't work. Changing link to point to /usr/share/ubuntu-artwork/home/locales-ubuntu/index-en_GB.html (for English) fixes the broken link, but it just points to the generic Ubuntu "getting started" page, not Ultimate-specific. [fixed-sorta]
[[[ EDIT ]]] - This was a problem with the combo Gnome+KDE version I was using. The pure-Gnome version works the way it's supposed to.
3. In Software Sources, the http://repoubuntusoftware.info repository points to "gusty" instead of "gutsy". Not sure if that's a bug really. I suppose it could be that way in the actual repo too, and if so, it's not, but the repo gives all 404 errors atm. [FIXED: It IS supposed to be "gusty")
4. No shortcut for KVirc in any of the menus. Running from a terminal will start it, which will then add a desktop icon if you want. [fixed]
5. Not really a UU bug, but an issue... Startup Manager will add /vga 792 at the end of the kernel lines in the grub menu. With NVidia cards, this will make it so you can't CTRL-ALT-F1 (or whatever) to a console. You just get a blinking icon in the upper left. Deleting that /vga 792 part from the entries in /boot/grub/menu.list fixes that. [fixed]
6. (Grub-installer issue, not UU specific) In systems with multiple hard-drives, the grub-installer can get confused. In my case, it detects the proper boot-drive as hd2, but when rebooting, grub itself sees it as hd0. This led to an Error 17 error. Changing the references in /boot/grub/menu.lst of (hd2,0) to (hd0,0) fixed that. [fixed]
7. I wasn't gonna post this at first cuz I don't know if it's a bug or not, but an Htop shows 60 separate incidents of "console-kit-daemon" running. I've tried around 40 different distros in the last month and I've never seen that before, so I figure it's GOTTA be a bug.
8. In the pure-Gnome version, the startup script that asks if you want to install adobe, flash etc runs in the live session, but did not run when I did my first boot to desktop after install.
[[[ EDIT ]]] - It ran on the SECOND boot, post-install. At the first boot, I disabled a bunch of stuff I'm not going to need... Bluetooth and power management stuff, MySQL and Apache and that mysterious "consolekit". No idea if it's related in any way, but after I rebooted after makin' those changes, the script ran the way it's supposed to.