That 2010 you raced must have a crappy driver or it is the standard gear GT. I agree with the OP. I drove a 3.31 auto 5.0 and I actually like my 3.73 2010 GT better. Yes, the 5.0 has more power (in stock form), but I was not "wowed" like I thought I would be. Maybe a 3.73 5.0 6 speed would "wow" me, but I'll wait until 2012.
You guys need to understand, from my point of view this thing is like a rocket going from a Challenger RT to a 11 Mustang 5.0. I drove a 2010 GT w/ 3.73 gears and the only difference was accelerating from a stop but it didn't feel much different than the '11. Acceleration while cruising, the 5.0 is way better than the 4.6. Besides couldn't see trading my Challenger for an engine which has run it's course and is now yesterdays technology, not to mention the 6 speed tranny. I have to drive 60 miles a day to and from work daily on GA400. I want the best of both worlds - lots of power and fuel economy - case for the 3.31 gears.
For what it's worth, about $4,000.00 will get power levels comperable to the 5.0 in the 4.6 - this is what is being done at our "speed shop" for those die hard 4.6 guys.