1) The X axis seems improperly inverted on my Macbook Pro running Leopard 10.5. When I tilt the left side of my laptop down the marble goes right (unexpected). When I tilt the back (monitor side) down the marble goes up (expected). Not sure if this is the JS app interpreting the data wrong or the app is getting inverted values from my machine vs. others.
2) When you finish a level (win/lose) the app seems stuck. You can't go back. Reloading the page takes you the welcome screen (pick an input). It'd be nice to have a "Try Again" button as well as one for "Main Menu"
3) I get the current interface, but having a preference selection for motion input like on IRC for notifiers would be nice. Then, the first screen can show all levels. If you don't have an accelerometer, then you could always make Mouse the input.
4) in the case there is an install/init error for BrowserPlus when the game starts up, it has a bad link to "/browserplus.yahoo.com" I think it's missing a protocol specifier or such. Also, you might take them straight to the /install page to debug the init error or to reinstall or to upgrade.