I had the opposite problem from you. The ddwrt doesn't work for me and drops wifi packets. I installed the 1.76 stock firmware and got really good results - I did have a bit of problem at first b/c I had set the SSID to the same as it was before and the same password. My mac and iphone were getting wifi failures etc in a strange way. They were connecting b/c they had the correct pw for the network but somethign was wrong (network type, encryption, something - I didn't take the time to find out). I just changed the SSID and password and packets went like wildfire across the stock firmware.
After that, buffalonas.com, upnp, remote access, bittorrent, etc were all fine as well. I did run 1.72 for about 6 months and the nas features were kinda crappy. 1.76 seems to work well.
If you have the time and patience, maybe give the stock another shot? If not, then I've totally failed to answer your question :)