Where I came from growin' up, it was cool to "jack up" the rear end of your ride and put big tires on the back... looked cool back in the 70's (yeah, I'm that old). Kinda like you were ready for a drag race at any moment. This would raise the back end tail lights of those old stangs, camaros, 'cudas, roadrunners, novas, etc a good 6"-12" higher than the norm.
Anyway, I was thinking the other day that the back end of the new 'stangs kinda look like someone jacked up the rear end like the old days. It's kinda' retro in an odd way.
Looking at it from that standpoint, it's not as bad. Still not my favorite, but better. Kinda' like when some guys (NOT me!) used to hang a second muffler off the back end of their car to make it look like they had dual exhaust when they didn't.
I think they look pretty good, IMO. Pretty impressive, actually. I don't see what the problem with the rear end is. Aside from the spoiler, it looks fine. Even if you hate it, the only people are going to see the rear end are the losers, so what do you care?
The front end has some serious overbite going on plus too much black plastic. The rear end looks like it should be on fat a55ed sedan, sequentials notwithstanding but you can get that aftermarket on an 09. The wheels invite serious curb rash if you are not experienced at parallel parking.
I do like the rear antenna having been moved from the front 'reach for the sky' antenna. As nice as the rear antenna is, it might not match the lines of the 05-09 if it were possible to switch.
The interior and its appointments would be the only thing that would sway me towards a '10. Ditto if fit and finish is better.
Personally, I would rather like a car on first sight rather than let it grow on me.