Actually I've tried the latest Ubuntu and still have it installed on a harddrive in my box. I dual boot it every now and again to show it to people.
I'm completely in love with the Compiz Fusion desktop and adore the Gnome user-interface. I found everything exactly where "it should be" without having to bother reading the help files to find the hotkeys. It was also fast and smooth on my box. I won't say anything bad about KDE, I just like Gnome.
The package manager was awesome - point, click, install, use. The Ubuntu update manager was also really nice. Everything I tried out on Ubuntu worked first time without needing any head scratching or fiddling in the shell.
But Ubuntu isn't stable on my hardware configuration. After installation it crashed after 30seconds to 2 minutes (not a graceful crash either - just a system freeze). I spent hours (2 or 3) reading the Ubuntu user forums for help and saw that it's a fairly common problem. I rolled back my nVidia drivers (3rd party, not Ubuntu's "fault") which improved my uptime to around 5 to 10 minutes.
I read that there are issues with Firefox in Ubuntu, but I'm not sure if I can replicate that yet and not running Firefox doesn't really seem to help my uptime.
The default Ubuntu installation didn't cope very well with setting up my Grub options so the thing wouldn't boot. I had to get Supergrub to fix things up.
Ubuntu is supposed to be the newbie's Linux and so I think my statement about Linux being user-unfriendly is something I'll stick to. I will back down from "terribly".
I think the next Ubuntu will be the one that gets me to swap permanently. I'm betting it will be stable on more hardware configurations and hopefully mine will be one of them.