I've got some older hardware, but I'm OK with this.
KDE is a heavier desktop, is designed for newer computers, and as such should keep a certain focus. If I want to run the older hardware, I'll run XFCE, LXDE, or E17. Which I'd likely do anyways.
On my main computer, I'll stick with KDE.
Some things are just going to have to change, and linux/OSS technologies are no different. Do you think you're going to run your Pentium II for the next 20 years?
EDIT: Oh, and about Catalyst, I've never had much luck with it anyways, no matter when/where I've tried it. I'd like to know what Bridgman and the boys are planning on doing to bring the OSS driver up to speed on this, if that's even necessary.