I would say you can leave it on, with minimal "play time" while it is going through its first full charge. I may end up just turning it off for the first charge, but only to "know in my heart" that I will get the best battery life possible. If that happens, I'll send out my hardware impressions, then software impressions.
Matt
EDIT::: Just talked to my personal Android "guru" and he said that we need to run the battery dry and then charge it COMPLETELY. He also threw in NOT TO MESS WITH IT while that crucial charge goes on!
That parts gonna suck,
Matt