Morrisville State College claims the world's first large-scale 802.11n network. It has 720 access points from Meru Networks. Capacity (speed) should be 130-150 Mb/s per basestation (shared). The MSC reports 1200 simultaneous users at peak times. It's still early days, but improvements relative to 11a/b/g are noticeable.
The report also mentions Duke University (a Cisco user) and Carnegie Mellon (which uses Aruba Networks and Xirrus gear) as 11n test sites.
I suppose this is the next step toward ubiquitous broadband, with any type of wireless technology for the last-few-meters. The WiFi camp will now be looking to add mobility (part of the 11r standard).