I think that Now on Tap is the most useful feature. Tried it on a preview build while it was still active and it blew my mind with how much context can change how you search for stuff.
I want one to give to my father. He's stuck with an 8GB Nexus 4. I don't see how anyone can use a phone with less than 7GB of usable space, but somehow he does.
Re: Cancelling the Sprint service and ICS update after cancellati
You should still get the update. My Nexus One got updates when it was wifi only. If not, there is usually someone who will post the update.zip link for the update. Then you can download it and manually apply it via recovery.
AFAIK, OnLive does not have a device check except for Play Store filtering. If you can't download it to the N7, download with another device and manually install the APK. It should work.