I was initially going to pass it up, but I might bite the bullet, I don't know. There isn't a killer app per se (if there was a Crimson Skies sequel being shown off, my money would be right on the table, absolutely ate up what High Road to Revenge had to offer and can't wait to see the landscapes and battles with next gen capacities), but there are some nice titles that I might have some fun with.
For launch window, there's Elder Scrolls 4 and Kameo (I owe it to a friend to pick this one up, he did some work for it). DOA4 looks pretty good, and I'm curious to see if the mutterings about Soul Calibur 3 being released for the Xbox 360 end up true. I'm also thinking about FFXI, since I'd be able to lug my 360 over to my sister's place and leech off her broadband, whereas on my home PC, I'm stuck at half the speed of 56k.
So there isn't really a killer app, per se, but the selection of titles looks decent enough.