I just got the new extreme and it sucks! It's so slow. When I do a speed test with my MBP plugged into the ethernet I get 3M/s when I go wireless best I get is 1.3m/s and I tried all the channels.
I am having the same issue, although I didn't have it 3 months ago with the exact same set up. I have hard connected to the DSL modem and its fine so I know its the AE. I have tried every setting and nothing helps. If anyone knows anything please post it. Thanks.