I'm using an N dongle with Ubuntu Studio 11.04.

Internet access provides no problem at all, but my home network
(Windows) does.
(This is being investigated.)

The Sitecom WL-344 dongle I originally intended to use wasn't at first
supported, but about a month ago it passed my test.
Apparently, an Ubuntu update has fixed this.
(I'm however using an older Sitecom WL-302.)

It's more a question of the manufacturers of these dongles not
considering Linux in general ( as usual !! ). The Linux community is
therefore left to 'pick up the pieces' and figure out how to get these
dongles working :-( This takes time unfortunately but there are some
makes that have been verified - check the list here which gives the
status of development for drivers plus the devices supported.

http://linuxwireless.org/en/users/Devices/USB

I bought a TP-LINK WN727N last year and had to bring it back since it didn't
work then but now it's on the list.