The Wikipedia says up to 540Mb/s, but most of the router boxes at the store today said up to 300mb/s. eWEEK says 130Mb/s, "Netgear's products proved to be the unrivaled speed champs at close distances—topping 130M bps of real throughput—but performance started to lag considerably as the client moved away from the router."
Distance concerns aside, 130Mb/s doesn't sound very fast. Then again, I'll bet my 802.11g setup gets no where near 54Mb/s.
Update: NetGear's USB 802.11n adapter does not seem to work with OS X. :(