Ok man, I just got done with the N adaptor for xbox. I used the cd that came with the adapter first.
I configured the 4500 for N mode only 5Ghz, Auto speed, WPA Personal-WPA2/AES only, and the adapter connected correctly. I played one online game with Black Ops with no lag or any hiccups. I then switched to G Mode Only at 2.4Ghz and did the same thing. Gaming was good. My router is one room over so signal was good. I saw 160Mb speed when I was on 5Ghz.
It also connected to my Apple Extreme router with N however I notice it only connected on A mode and not N. I can't use n only on the Apple so I presume it would however I guess the A mode was preferred.
It also connected to my NetGear 3700 with DD-WRT FW loaded thats setup for 5Ghz N mode only AP bridged mode.