I had 3.1 running on an old P1 133 laptop for a week or so. It ran rather cleanly, a lot less kludge than the comparible releases of RH7.1 and Mandy8.0. I especially liked the solitaire game it gives you during package installation.
My biggest complaint was that when I botched the XFree config, it just kept trying to restart X, no timeout on X crashes. There was no way to kill it, and since I didn't know Grub back then to force it to runlevel 3, I had to boot with an floppy Linux to fix it. Aside from that little dementia it was a nice system for the time I used it.