This is the infamous 802.11n Sarbanes-Oxley mandated $1.99 802.11n enabler.
These benchmarks are crude, but should give you a rough idea. All benchmarks were performed with a MacBook Pro 15" Core 2 Duo, a 'snow' 802.11g Airport Extreme Base Station, and the new 802.11n Airport Extreme Base Station.
crwdns2944171:0crwdnd2944171:0crwdnd2944171:0crwdnd2944171:0crwdne2944171:0
crwdns2931507:0crwdne2931507:0
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crwdns2931511:0crwdne2931511:0
crwdns2931513:0crwdne2931513:0
crwdns2931515:0crwdne2931515:0
crwdns2931517:0crwdne2931517:0
crwdns2931519:0crwdne2931519:0
crwdns2931521:0crwdne2931521:0
crwdns2931523:0crwdne2931523:0
crwdns2931525:0crwdne2931525:0