To see a speed increase you'll need AC capable adaptors on your computers. If you do, the claim is 3 times faster than wireless-G. That should be noticeable on complex sites like the Weather Channel, but especially on large downloads. I've downloaded several ISO files for versions of Windows 7 and 8 that take 20-30 min. even with my Comcast cable connection. Of course as you point out, wireless connections between computers would be faster as well. It might even make it practical to do system backups wirelessly; it's sure not with wireless-N. I backed up a 14 GB partition with wireless-N yesterday, and it took 80 minutes. The connection had 5 bars FWIW.
I'm in the market for a new router. I have a mix of Windows and Mac products in my house so need support for both platforms. I am considering the new AC routers that have hit the market just so that I will have that support down the road. As I look at all the quotes of blazing wireless speeds, it brings up the question... where will that additional speed be noticed? I don't believe it will make my internet connection any faster. So will the additional benefit only be noticed when one device shares with another on my network?