I'm also running 9.1 / KDE3.3 quite happily on a 400 MHz Celeron with 256 MB RAM, something the author suggests is bogglingly slow - I'm as impatient as most, but find performance adequate if not stunning. Mind you, I'm not using that particular machine that much ... I don't think Mozilla, and certainly Firefox, is slower than IE. I notice much of his serious moaning is about Gnome, about which I can't really comment because I've only used it in Sun's version on SPARC machines. Where it's not specially nimble, I have to say, but maybe that's the Sun implementation.
I have you beat there -- I'm running 9.1/KDE3.2.3 on a Celeron 366/196MB laptop. I've turned off various things I don't need, but it runs a LOT faster than Windows XP does on this machine. Steve Kratz