Known issues and MPG with '07-'10 impala

I am looking at buying a '07-'10 impala with either the 3.5 or 3.9. Can you guys fill me in with some of the known issues, things to watch for, and mileage. Thanks.

Well I guess I will throw in my two cents.
My GF has an 07 with the 3.5 engine and it is a stong running car that drives great and is quiet. No mechanical issues in 40,000 miles. Fuel economy is 28-29 mpg.
I have an 07 Lacrosse that is pretty much the same car and I have had transmission and engine issues that were corrected under warranty.
I would not shy away from buying one, they are darn nice cars.

I have an 05 Impala that gets 27-29 on the highway with a 3.4 base engine.

Great cars! Just keep your foot out of the injectors.

2008 2LT with 3.9 engine. 108,000 miles and the engine has not missed a beat. Mileage of 24-28 per tank depending on how heavy a foot you have. Only issue is replaced both rear door lock units as they would not work consistently when you activated the locks.

The only MAJOR things to look out for is Rear Tire Wear due to Bad alignments from the factory (if the vehicle has never had an alignment after purchase) and the transmissions are still flakey on some once you rack up the millage (good O'l 4T65E). The only other things I can think of are Poor Range on the RKE (06-07 only I beleive? had this problem), Rear defroster shorting out due to under-sized pin in a connector (easy to fix) and Blend door motors failing (another easy fix).
Personally The best I've gotten MPG wise was 27mpg after 150 miles on the hwy with the wind pushing me.

Well HeMi is right about the alignment. If you have one of these cars and think it drives nice, get a four wheel alignment and there is a big difference on how it drives. I thought my car drove good but after the alignment it is a different car and I love to drive it even better than before.