I own a K7N420, which is stable, but you might have trouble running high-powered vid cards (ie. GF4Ti) on it. The A7N266C seems to be a great board from what I've seen: stable, good overclocking results.
I should mention that there are two nForce chipsets available now: 415 and 420. The only difference being that the 420 has the onboard GPU and is slightly more expensive. If you are worried that you can't use the AGP on the 420, you are wrong. The BIOS automatically disables the onboard GPU upon detection of an AGP card.
MSI also makes a 415 based board.
If you want real, factual information from educated persons, I suggest you go to nForcersHQ
. There you will find the largest group of nForce owners anywhere on the web.
edit: Oh, one thing I forgot to mention is that nForce is notoriously instable on Win9x.