From what I understand, 5ghz networks are much faster, however their range is only half as good. Looking at apple's tech specs, it doesn't say if it supports 5ghz networks or not.
It's been a while, but I remember setting up my Time Capsule to the 5ghz N setting and my iPad could connect but my iPhone couldn't so I reverted back.
I don't have my iPad (one more day....) so I can't test it to make sure my memory is correct.
I have a dual band router, my iPhone connects to the 2.4 Ghz signal whilst my ATV2 connects to the 5Ghz signal. I will try it with both however Im guessing it should perform better on 5Ghz at shorter ranges.
If you're only using it for internet not many people will have a connection fast enough, but this is a network - people use it for all kinds of stuff.
I'm looking to upgrade my router to a fast dual band one, and my internet is a leisurely 6Mbit. Problem is, all my backups go over wireless now, from 3 different computers - and it's getting *slow*.