300mbps sounds wonderful, but not with my horrible Comcast internet connection.
I doubt there's an internet connection in America that even hits 54mbps. So I'm guessing that the only reason someone would be inclined to upgrade is for faster data transfer within the local network.
With my internet connection where download rates are rarely ever above a few hundred kilobytes a second, would I even see any improvement in switching from 802.11g to 802.11n?