There's a ton of information out there on 802.11ac, and at least two tons of opinions. Here's a sample from Network World and other sources. Feel free to jump into comments and share links to stories, blog posts, backgrounders, videos and the like that you've found helpful in getting a grip on "Gigabit" Wi-Fi.
802.11n products will remain the core of enterprise WLANs for some time to come. See our March 2012 Clear Choice Test, by Craig Mathias, of three-stream 11n access points: "Three-stream Wi-Fi hits the mark." Mathias has a sidebar on "What you need to know about 802.11ac" to give you some perspective on the relationship between the two.
Perhaps the most important feature of 11ac is that it works only in the 5GHz band. From October 2011: "Wi-Fi devices crowd 2.4GHz band; IT looks to 5GHz." The new iPhone 5 is one of the few smartphones that has added 5GHz Wi-Fi: "FAQ: iPhone 5 and 5GHz Wi-Fi"
AnandTech's "5th Generation WiFi: 802.11ac, 'Gigabit' WiFi Primer" from January 2012
Some details on 11ac beamforming: "Beamforming: 802.11ac promises great Wi-Fi enhancements, but you can get a jump today," by Bart Giordano, director of wireless marketing at Marvell Semiconductor
At Mobile World Congress 2012 in February, vendors were beating the drum for 11ac: "Speedy 802.11ac Wi-Fi set for fast, wide rollout"
11ac product news
PCWorld's 11ac review: "Who makes the best 802.11ac router? We review the only 5 models available today"
Webinar: "802.11ac Gigabit Wi-Fi: Fact vs. Fiction," with wireless consultant and Network World blogger Craig Mathias in an Aruba Networks-sponsored webinar about 11ac
Webinar: "802.11ac Wi-Fi Demystified," a tech overview with wireless consultant Avril Salter, sponsored by Meru Networks
Related: "Wi-Fi client surge forcing fresh wireless LAN thinking," from June 2011