I managed to ride it once yesterday, in the front-middle (row 5).
So I can safely say that the middle is good, not great. I would've rode more, considering the line for the seasonpassholder/members was VERY short... the ride brokedown for over an hour while we were waiting in line, and the 10 minute wait turned into over an hour wait, and considering we had somewhere to be we unfortunately only rode once.
I've heard the backrow is fantastic so I cannot wait to give it another go, but of course you can't choose your seats so it is unfortunate.
So as a one-time middle rider; my review is the ride is good in the middle, not great, not mind-blowing, definitely slow in the middle, and the air-time is meh at best. The stall and turnaround are still very good in the middle though!
I'm sure the GP would be perfectly satisficed with the middle, but for me; a coaster nerd who's been on many many roller coasters, I think that this ride is simply good in the middle. But definitely cannot wait to ride in the back because I've heard the airtime is incredible!