Seeing as offline times can be re-submitted
Sorry for the awful bump, but do you mind elaborating?
For having seethed with rage after I realised that I did the cotton alley dark world levels offline, the prospect of being able to submit those times without having to do the bloody things again is rather appealing.
Whenever you complete a level, your best time (the one listed on the level select screen) goes to the leaderboard, whether or not it is run you just completed. That's why Meat Ninja times upload to the leaderboards once you complete the level again (XBLA).
It won't help you much though--if you want your offline times to upload you'll have to beat all those levels again
(but at least the better of the two times will go to the leaderboard).