I have mine set to:
802 band: 2.4ghz
Auto Scan: Checked
Tranmission rate: Best
Channel Width: Auto
When I have it set to G or N and G, it connects at 130Mb and gives me about 32Mb of a 50Mb connection. When I set it to N only I still connect at 130Mb but get about 40Mb of a 50Mb connection. This is on a XP SP3 laptop with a Intel(R) WiFi Link 5100 AGN from about 3 feet away. Also, I have about 20-30 wireless networks in range, most of then FIOS Actiontec G networks, and my router usually scans and 4 and 8 as the best channels. Where you start having issues is when you start dropping below 60% signal strength. Try to use extrenal adapters or adapters with external antennas to keep your signal strength above that and it won't be as much of a issue, but as a whole I have no problems running my Ipod touch on G, PS3 on G and laptop on N. Most of the time I keep everything wired though. Hope that helps