I already use Ubuntu and have done for a while now. I didn't know anything about LInux a year or so ago but was working with a chap who was a Linux geek and he put me onto it. First I put Puppy Linux onto an old and beat up HP laptop. It was running Win98 but I spent £20 to up the ram and Puppy ran like lightning on it. It has since run Ubuntu 8.04, and it now has 10.4 on it but it's a bit sluggish, but the laptop is 10yrs+, so no shock there. With the new release of Puppy 5 I'm going to stick that on it and see how it goes.
On my main desktop I was running Win7RC, but then the PC died and I was looking to get back online on the cheap. I went out and got a bare-bones unit for £140. Stuck in a graphics card for £25 and upgraded the ram from 2 to 4Gb. My next problem was getting an OS up and running. I didn't have a legal copy of windows that I could use and I wasn't about to pay for it, so I gave Ubuntu a try and I've been using it ever since. I have to say that there hasn't been a moment where I've missed windows. I don't have an ipod so I'm not bothered about itunes and for everything else Linux has it covered.
As for 10.4 I like it but my PC doesn't. It's nowhere near as quick as it was with 9.10 and this is a dual core 4GB unit, so it should fly, but for some reason it doesn't. I do find myself staring at the screen saying "come on then, do something". Maybe I have a duff install? I might download another iso and try again.
I like the way that 10.4 looks. Lots owed to the Mac for that but that's not a problem for me (I'd have a Mac if the hardware wasn't so bloody expensive).