This bug is insane. I tried to make some sense of all the comments, and there are *at least* three unrelated problems ...
Problem #1: "my skype connection is randomly interrupted and using wicd fixes it"
This is likely caused by background scanning not going as smoothly as you think -- I believe most versions of NetworkManager still scan every 2 minutes, but there were improvements in this area.
Problem #2: "my router crashes when I use Intel's card" (see comment #24, comment #34)
This is a bug we've investigated and we think we fixed it in commit 59f53ce22e, upgrading the kernel to 3.0.0-13.21 (ubuntu version) or 3.0.6 (stable version) should fix it. I'd love to see this tested again, but it seems unlikely that there are two bugs that both cause some APs to crash (I'd HOPE not, but some APs are notoriously shoddy quality...)
Problem #3: "my 11n connection is really slow, disabling 11n helps"
This is puzzling, and since I've never seen this anywhere I'm starting to think it might be a combination of the router/AP & environment used. Anyone near Portland, OR or Bielefeld (Germany) where we could debug in person? :-)
Problem #4: "my connections are dropped frequently"
This might or might not be related to #3, but I can't really tell.
Generally, it would be nice if the commenters would include more details about their setup, like the exact kernel version (ubuntu package version number), and, if possible at all, the model of the AP. Thx!
I'll continue monitoring this bug report for a while but with the volume of reports I'll have to devise a debug strategy first ...