I don't seem to reach a distance problem with mine anywhere in the 1500 sq ft house I'm in... (luckily I've got a nicely centralized location for the server) I do however have 2 areas that give me problems.
1) in the kitchen where a wet wall (where all the pipes run) and a very metallic fridge are probably to blame
2) when secondary WAP is directly below my main WAP (I'm sure if I adjusted the antennas properly I could get this to work, but I just gave in and used HPNA instead)
As far as actual distance, I guess the furthest distance I've actually gone is around 40ish ft, luckily just about everywhere in the house only has 1 wall between it and the main WAP
It's been way too cold and icy to risk my receivers outside lately... maybe once it warms up and the deck outside gets built...
(By the way, this isn't quite at 320kbps, large part of my collection is ripped at highest VBR setting)