If you're getting an automatic, you probably won't notice much of a difference between the 07 and the 09. The 09 doesn't really feel any faster to me than the 07 did but the motor is a little smoother and fuel economy is better. Now if you were looking for a 6MT, get the 09 as they have improved the clutch.

 

Personally, I think the clutch is too soft and the point of clutch engagement is too late. The clutch engages after the clutch has been released halfway. My 300zx had a clutch that engaged about 1 inch after I start to let off my foot.

+2 on the G35. I had a G35 loaner and was always impressed when I floored the car. You won't miss the extra horses that the g37 has.

 

I had a G35 Sedan Sport and just got a G37 Sedan Sport, both manuals. I can't say much for the sludge box cause I've only driven those when they gave me a loner but if money is an issue you can't go wrong with the G35. The G37 is more refined and you'll feel that more than the extra HP. The shifter is smoother in the 37 too. Still, the G35 is a hot car and won't disappoint. Haven't had it long enough to notice the mileage.

Get a spoiler on it though.