I drove both & selected the 4.8i. Gas mileage has not been great (14.8 60/40 urban/highway), but the vehicle is still in the break-in period so I expect that will improve a bit. The 4.8 definitely has plenty of power & I have never experienced any hesitation while the system adjusts to my driving style. The 3.0 demo I drove felt considerably less powerful (not terrible, but not anything like the V8).

Yes the sport mode (button) only deals with the suspension. However there is also a sport mode for the transmission (slap the stick to the left and you are in it.) "Manual" up & down shift and a more aggressive mapping of the throttle response.

Probably a sacrilege to mention this on a BMW board, but my wife drives a Lexus 400h (hybrid), great acceleration & much better for the environment (not nearly as much fun to drive though!)

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2008 4.8i Mineral Green Metallic Sports Package, Technology Package, Cold Weather Package, Rear Climate Package, Premium Package, Premium Sound with iPod adaptor & Sirius Radio, Auto Tailgate, Head up display