Do your research before you buy. Wireless card vendors change chipsets
without notice or obvious version rev's.

Stay away from the Realtek 818x based cards. The driver is broke in Gutsy!
https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.20/+bug/78255

In general, I recommend cards with the atheros chipset.

Note: My comments are related to wireless cards in general not to USB
specific devices.