Is there any new rulings on the text of Stealth Bird? I was told at a tourney today by some players that if you flip summon him in the main phase 1 that you could only flip him back face down again during your main phase 2. Is this right? I figured I could just do both in the same main phase.

You are correct, Stealth Bird, or any monster with a similar effect, may be flipped face up and then face down during the same main phase.

You're thought is correct.

See...the people that told you that are only half right. They are wrong in the fact that you "must" wait until Main Phase 2 to flip it back face-down if you Flip Summoned it during Main Phase 1. It does not specify that it must be done during your "next Main Phase" or anything. So it can, indeed, be used during the same Main Phase that you Flip Summoned it (as long as you didn't use the effect that turn already).

Though, using the effect to flip it back face-down MUST be used during your Main Phase 1 OR 2. Not during any other phases of gameplay.