My Infuse works on my brother-in-laws Wireless N 5GHZ network.
It's like the 2nd or 3rd device to even discover that band in a sweep. The iPad 1 found it when iPod touches (gen 4) and iPhone 4's and even my Evo 4G won't discover that network.
He's got the NETGEAR RangeMax Dual Band Wireless-N Gigabit Router WNDR3700. <- I would know. I hand-picked that router for him.
I have to say, from a user perspective, haven't really noticed a range or speed improvement on N 5G.
Actually clocked higher mbps on the non 5Ghz channel. Think I was connected at 64-65 mbps with like 20k down and 5k up.