It just worksHaving tried and returned (and possibly breaking) a number of dongles i finally found one working out of the box with Ubuntu 12.04.
It's really small and simple and connecting it just makes all surrounding networks visible in a flash. Had it running for a couple of hours and done numerous speed tests on bredbandskollen.se measuring some 55 Mbps (on a 100 Mbps line). Same result on a second computer (Ubuntu 11.10).
The KÖNIG (KONIG) Electronic USB 300 Mbps WLAN Dongle / Ultra compact adapter can be found in Teknikmagasinet (Gallerian, Stockholm) for 199 SKR and CDON for 219 SKR.