Hi guys,
First, thanks for this awesome thread and we're so glad you're having fun with the game!
Couple things - the XBLA servers were *overwhelmed* at times during the last 12 hours but Microsoft has quickly deployed more hardware to address the issues and things are getting back on track.
Second, there are some known issues with the game, largest right now being Multiplayer Leaderboards not recording scores properly and sometimes resetting your progress. It is a known issue and we're working on it!
I can't provide help for other issues here on Neogaf, but please feel free to visit this KNOWN ISSUES thread on our Forums, for workarounds, known issues list, and reporting.
http://www.redlynxgame.com/forum/viewtopic.php?f=77&t=8047
It's also a good place to find deep discussion of track building, tutorial videos, and more
Thanks for riding and being one of the 100,000+ Day One players!