For the record I looked hard for a 2011 or 2012 Mustang GT. It is tough to find one, or if you do its the color that makes it hard, and because of that I found the dealers weren't to into the dealing mood, knowing they could sell it regardless. The old supply and demand at its peak! I was also looking for an automatic. I found a few manuals but after driving them around all day realized how shifting in traffic becomes a PITA. Camelback Ford has a NEW stripped Grabber Blue with cloth for pretty cheap, they also had a white loaded 2011 they were willing to deal on, but it was used. In the end if I wasnt going to get what I wanted, which was 2012 Ingot Silver or a 2011 Sterling Gray GT I decided to settle for the 2010 and just enjoy the look and feel of the new body style.
So I bought the 2010 just because it looked like the 11-12 and figured I will have enough equity in the 10 that when the newer GTs are slightly less popular, or more readily available, then Id go after an 11-12. This allows me a new car again in about 18 months!
My wife should love that idea when it happens. At this point I'm thrilled with the 2010, it feels faster than my 06 and a lot more stable on the road, less cheap feeling, I also like the Microsoft Sync, which I didn't have in the 2006, and love the ambient lighting with the door sill lighting.
If your not in a hurry take your time and get what you want! I'm a little less patient. If the 2006 had not been a clunking bump machine I would have held out longer.

Knowing I'm going to get into a 2011 or 2012 down the line gives me something to look forward to. Having the 2006 fully paid off helped tremendously for any future Mustang I want.