I've got FreeBSD on a P11 350 192MB RAM,2 UDMA33 6GB HDs. Also have it on a Celeron 400.
I've got KDE and Fluxbox on the PII.
KDE does run fine on it but slow. So I use Flux on it most of the time. If you want the big heavy KDE on it, it will run without any problems but Firefox for example will take about 20 seconds to load first instance. Evolution will load too eventually.
Open Office your probably not going to be willing to wait for. Konqueror as a file manager will open the directory tree eventually. Running BSD-KDE on a PII is about like win 98 used to run on one, although a lot more stable.
If you were to run Fluxbox, Sylpheed, Nedit, Rox, Xmix, AbiWord, Xclipboard, Xcalc, Xnview, etc. you wont mind using the machine. It'll be a older but nice to use machine. The Celeron, it's slow even with Flux, but usable if that's all you had.