I think there were some xbox live server issues earlier, despite the green status. Some were reporting not seeing anyone online and also seeing their account having 0 gamer score. The online forums were not able to load gamertag pictures, stats, and anything related to a user's information on the posts.
Some reported having to do the following to get things going:
1. Go Offline -- Settings / All Settings / Network / Network Settings / Go Offline.
2. Restart -- Settings/ Restart Console
3. Go Online -- Settings / All Settings / Network / Network Settings / Go Online.
I hadn't had a chance to attempt playing online, but when I started up the console the H5 Update was already downloaded and installed. I saw BTB available in the Arena menu, but have not tried to play a match.