I run Tomato on a Linksys wrt54gl router in the basement of a large house. Signal was decent throughout the entire house. I got an iPhone 3gs last xmas, and it sometimes had problems connecting in our bedroom ( maybe twice/month?)
With Tomato, you can adjust the transmit power of the router, I think stock it's about 60% of max strength... I tweaked it a couple percentage points and have gone months now without a problem.....
Funny think about it is... the router seems to 'hear' the iPhone fine, maybe the advantage of having a bigger antenna.
Panny 47wx52, DMR-e80*C DSR500x2, XBOX 360, Toshiba 26hf84, LG 37LC2D