Just to add my .02 to this thread... I've been running 4.08 gears in my Z for about 6 months now and love them. Acceleration is GREATLY improved. I don't notice it much now since I've had them for a while, but I'm sure if I were to take a spin in a Z with stock rear end, I would notice.
My gas mileage dropped 2mpg... But I do have a little bit of a lead foot shifting at around 4-5k each gear.
SRM works, but not as good as with the stock rear end. Downshifting while decelerating is smooth.. Anything else is a little "jerky" until you get used to it. Also during high speed runs (120-130mph+) the SRM will shut itself completely off and won't come back on until you turn the car off for a bit then turn it back on. Not sure why... Not a big deal.
Top speed is hardly affected... I can still hit 140mph easily (and quickly) with room to go. I don't have big enough balls to see what the speed is at red line in 6th gear... But I know it's FAST.
Traction was definitely an issue with the OEM Bridgestone RE050's... Even with 305's in the rear. Since I upgraded to the RE-11's... I hardly have any traction problems and the car pulls like a freight train. Best tires, in my opinion, hands down.
That is all...
