I'm also going to echo this- I've done only a bit of playing around with Ubuntu, but with mediatemple downtime issues I was having (grid service is not quite what they advertise) I decided to jump in and get a slice about 2 months ago.
I couldn't be happier. The tutorials (especially the ones for Ubuntu) are fantastic, and setting up your server and security with shorewall/etc couldn't be more painless. I probably took only an hour and had apache/php/mysql and rails up and running securely.
Major points to slicehost for the high quality walkthroughs- and for 20 bucks a month, it's more than worth it to just get a slice and jump in. That's something I'd highly recommend (No, i don't work for them, I'm just very happy!)
I'd like to second the recommendation for slicehost. Great, honest service and the tutorials are good even for those of us who think we know what we're doing.