For a basic budget system, the K7S5A is hard to beat. However, if you intend to do major overclocking, this wouldn't be the board to get since it lacks voltage/multiplier adjustment, and only has limited FSB speeds. The latest O/C bios adds more FSB speeds though. Feature wise it is pretty complete, performance lies beneath the KT266A boards, but above the KT266 boards. If you're willing to spend a bit more for better performance, consider the VIA KT333 based ECS K7VTA rev3.x
I have both boards in 2 different systems and they're both stable 24/7. If you decide on the K7S5A, make sure you get the newer versions, since AFAIK the original versions had compatibility issues with Athlon XP processors.