I live in a student co-operative with 150 people. As part of my workshift responsibilities, I help people with computer problems. I'm no expert (another student runs our servers) but I know enough to keep people's laptops and the co-op's desktops running.
Anyway, we have three public computers. Our faster AMD K7 uses Ubuntu and gives us few problems. Being located in the dining hall, however, it mostly gets used for web browsing. Our Evo machine is hooked up to the TV and plays movies from the servers (which now both run Fedora Linux; one used to run OpenBSD but it died so we got a new one) and runs Windows XP. Our main public computer, an old 500 MHz Pentium III with 384 MB of SDRAM, runs Windows XP, and is in the study room.
The two Windows machines give us 99% of our trouble. They're used more (especially the Pentium III) but even considering this and its older hardware it shouldn't require as much maintenance as it does. One fails Windows Genuine Advantage (yet passed activation) and the other might fail WGA at any time, since I lost one of my CD keys and had to use it on a third-party computer. That computer, using the same key as the Evo box, wouldn't activate.
So, I've decided to put Ubuntu on all of our public machines. It's very, very easy to restrict access to non-administrators and has proven at least as usable as Windows in the dining hall. Plus, accessing our servers is easier in Ubuntu's GUI than the Windows GUI.
As for the Pentium III, I have no clue which distribution to put on it. I'd like it to run Word, but that's generally slow on Linux anyway, and might be unbearably slow on a Pentium III.