Yeah it really is a cool feature, I like how you'll be able to eventually browse the selection right from the couch. It almost seems like an insignificant upgrade but I actually used to think that it was a little bit of a pain in the ass to have to browse from my computer 
. Just wait though, you'll be jaded after a while. For the first couple of months you'll be burning through all the stuff you like and after that it's like.......ok, what now. That being said, I'm still happy to fork over $8.63 a month for the service. I imagine that the library will continue to grow. Hopefully they'll be able to offer some of the newer titles for streaming too.
No doubt that MS is doing a lot right with all of this extra stuff. I was really impressd with the announcements made at E3 regarding things like Netflix and 1080 movies and the games on demand. Like I said above that it seems like little incrimental upgrades but they all add up to something bigger that makes me happier and happier to own a 360.
I LOVE paying for Xbox Live! I also love that my love for it pisses off so many people.
