I will soon get an 100Mbps Internet connection so I have tried the throughput on some different firmwares on my WNR3500L to make sure that I don't get a bottleneck in the router and the results were a bit surprising. (WAN to LAN results):
Original Netgear firmware V188.8.131.52_31.1.25: 240Mbps.
Tomato K26USB-1.27.9047MIPSR2-beta16: 225Mbps.
DD-WRT v24-14826-NEWD-2_K2.6_big: 80Mbps.
OpenWRT Release 21May10 Kamikaze 8.09.2: 40Mbps.
Tomato is OK but why are DD-WRT and OpenWRT so slow? Is it possible to do some tuning to boost the throughput? I could clearly see that the CPU-load was the problem on OpenWRT.
The test were not very scientific, just copying a 200MB file using FTP between ram-disks on two gigabit connected hosts. The measured speed for the same copy between the hosts without the router was about 850Mbps.