from what i've read of comparisons between the man and at, the difference in acceleration is minimal .2-.5 seconds in the quarter mile and i'm not sure about 0-60. a reason why i'm curious is because i currently drive a tsx (awesome car) but lacking in torque being a I4. the difference between the man and auto tsx is quite significant. a full second in the 0-60, and somewhere near 1.5 second difference in the 1/4 mile.
i know you can't compare the satisfaction of driving a 6spd manual to the auto, but for those who buy the 6spd specifically so as to not lose a lot of performance, is the at transmission really that good or is it just because it's a v6 the torque makes up for the minor loss in power of an at car?

 

Its both. The auto in the G35 is especially strong because it was developed for the v8 VK series and seem to be very efficient with only 2% more powerloss than the manuals. The torque in the G is also plentiful enough to take advantage of the gear ratios in the 5at.

Also, RWD auto trannies are usually better than FWD transaxles due to the miniaturization required to fit all the components in the front. Hope this helps.