I like Ubuntu. I'm really getting comfortable with working in Linux; there are less shiny games to distract me (once I uninstalled the several dozen games that come with Gnome), if I have a problem I can usually hack on it until it goes away, and the development tools actually work. Gold. Every couple of days I discover something new that I like about the system.
I only have one gripe. This may sound minor and petty, but considering how easy it is to customise the rest of the system, this is starting to get on my nerves.
If you move the mouse over the task list and scroll the mouse wheel, then the windows switch. This is annoying. Every now and then I'll be scrolling something and my mouse will slip a few pixels down and WHAM where did my window go? Cue a couple of seconds disorientation while I figure out which window I was in and click on it again. Oh, and it completely fubars the task switch order, so if I want to alt-tab back to another window I have to actually pay attention to where the window is in the queue. I do this a lot; it's very common for me to use two windows, one for coding and one for compiling for example; so this really irritates me.
The mouse wheel shouldn't do anything on the task list. That whole rectangle of screen space should be a dead zone as far as the mouse wheel is concerned.
It wouldn't be so bad if it was actually a useful feature, but it's not. At least with my mouse, it's impossible to control properly. In order to get enough traction to actually make the wheel move, I usually have to pull it so far that several wheel movements register all at once, causing windows to go flickering all over the place. Utterly, completely useless.
There's a bug report from early last year for making this behaviour optional. It's listed as a "wishlist" feature, and the upstream bug is listed as an "enhancement". I'm not holding my breath.