Personally I think Ubuntu is great, probably one of the better distros of Linux that I've seen to date. The only problem I've run across is that it doesn't want to play nice with my Inspiron 9300, but that's not specific to Ubuntu; I have the same issue with SUSE as well, so mod me down if you think it's a dig (which it's not).

(As an aside, Ubuntu "Live" was great for testing out that OS X x86 release that was going around, so in that regards, kudos to Ubuntu for being straight-forward to provide the means to get OSx86 up and running.)