Well, here's my two cents. I've probably watched Griffin play 20 games between last year and this year. He's played against very good competition and consistantly put up very good numbers. I've seem him block shots and have his elbow above the basket, so I know he can jump. He has good foot speed and he has good lateral movement. I think he's a pretty good athlete, but a deceptive one.
He tends to do just what needs to be done. If he needs to move quickly, he can, but if he doesn't, he won't. He playes totally within himself and does only what is necessary to get the job done. Thats why you have to watch this guy a lot to get a good read on him.
Now if you want to draft a guy like Thabeet, that puts up decent to good numbers againt weak competition, and struggles against the occasional good competion, instead of a guy that consistantly puts up good numbers, against good competition, night in and night out, go right ahead. It flies in the face of logic, but you go right ahead.
As far as his height. Its impossible to tell on television how tall someone is. There's no depth perception on tv, and angles can at times make a guy thats 6'3" tall, look the same height as someone 6'9" tall. So I suggest we wait for the pre-draft camp measurements before making any judgement.
I think the guy can play in the league. How good he'll be is up for grabs. But thats true for any rookie. Oden isn't exactly tearing up the league right now, and there are fans in Portland that are second guessing that choice. I'm not! I think he'll be a very good player. My point is that there are no guarnantee's.