Bynum is legit. Regardless of the Suns defense, he showed he has great touch around the basket, good hands, a credible passer already, and a hard worker. He works to get good position (not just this game but the pre-season as well), shown himself to be at least a competant rebounder and doesn't give up on plays.
To draw a comparison to another young bigman people here are familiar with, he's younger, taller, longer, faster and all around better than someone like Jackie Butler, which he should be considering he was a lotto pick and Butler was undrafted.