If there's one valid complaint about the K7S5A it's that you're very limited when it comes to overclocking. However, CheepoMan's hacked BIOS gives you a few options, and yes I did overclock.. I had my 1600+ running at 1540mhz and it was rock solid.
As for RAM, I ran several different memory configs on my K7S5A. First off I had 256mb of generic PC2100 (which worked flawlessly), then I added 512mb of Kingston PC3200 (and it continued to work fine), then I swapped out the 256mb with another 512mb stick for a total of 1gb of PC3200. I never experienced any kind of problems with any of these configurations, even when overclocking.
One thing that you might want to look into if you're having trouble with this board is your power supply. I found with my old generic 300w PSU I had plenty of problems, but when I installed a nice Enermax 350w, everything worked just fine.