You might want to check out the DD-WRT thread in Networking, someone there said he had a Buffalo 300N router, and had issues with various DD-WRT builds. So you might want to hold off before flashing.
Me, I've been running older (12xxx, 14xxx) DD-WRT builds on my N routers for years, and they've been rock-stable. But I haven't tried any of the newer builds. Also, I'm on Broadcom hardware, which my understanding is that the wireless drivers for those are more stable than the Atheros drivers, which might be what the Buffalo uses.