For those of you who were having issues installing the GUI using the installer, the problem is FIXED.
You should be able to download the (windows version) software just fine from the downloads page, and install it with no problem. A couple things that makes using the installer better than extracting which is why I went this route with it was because of the ease of installing, and actually allowing it to be uninstalled without you having to waste your precious time finding out which files need to be removed. The GUI will place a start menu entry with an uninstall file, or you can remove it through control panel! If you come across any bugs, please let me know, and enjoy!

Cool. I tried installing it last night and it wasn't working. I'll try it again, thanks!

where can i find what it looks like before i install it?

viewtopic.php?f=98&t=39177

Has screenshots in that thread.

Is my CSS background supposed to be purple squares on the main menu?

I've noticed two issues with the GUI. First, on occasion when clicking "Disconnect" from a server, the game will crash. This never happened to me when running the original GUI and only started when using the n00bfest GUI, but it's pretty rare. Second, there is no link to the achievements page like in the standard GUI. This means I have to uninstall the GUI, edit what achievements I want showing on my screen, then reinstall the GUI.

There never was a link to the achievements, in the GUI, ever.
I'll take a look at the disconnect crash, though, and see what I can do to fix it.. there should be another patch coming for it as well, to remove some unnecessary server IP's, etc. Thanks for your interest!

There is in the regular GUI, it's really handy and something to consider adding when patching the GUI.