Nav + gadgets are MUCH MUCH better on the G37 -- hopefully someone will write something up. I've been meaning to but haven't hard time. BMW really needs to get that act together on that one. I recently sat in my friend's G35 and the nav system is really about 10x better. The BMW nav is very rudimentary.
Some simple examples that I remember (there were a TON more): the G37 will superimpose traffic info on the map itself with colors to show traffic (like Yahoo maps does, for example). A lot more stuff is customizable. It shows brands of gas stations with little icons. Lots of stuff like that.
But yeah, as usual the driving experience in the BMW is better.
But that gap is shrinking each time around... The driving experience gap is a lot smaller than the gadget/navigation/price gap, that's for sure!