Having owned an '07 G35x 5AT and an '08 G37S 6MT coupe I can honestly say the E60 is miles better than either. I'm not regretting getting the 6AT on my 535xi at all - the shifts in normal D are as good as I'd like and DS works like it's reading my mind. The 6MT on the Infiniti was like rowing a broomstick handle through a bucket of rocks and the clutch was nearly impossible to modulate. All of my BMWs prior to this car were manual and they always had the smoothest shift and best clutch takeup of any other car I've tried.
Congrats on your purchase - you're going to love it.