I'm picking my F15 up next week and will drive it 600 miles back from the dealership. Should have some good comparison summations to give after that. I have test driven the gas version of the F15, so I'll leave out the driving/quiet factors.
I am a huge fan of the upgraded technology. I'm a fiend for new tech and BMW got me hook, line, and sinker with this model. The voice control never worked well in my E70, but I haven't tried it in the F15 yet. I'm also hoping the Bluetooth & USB benefits are a little stronger this time around. Drawing letters worked superbly for me.
The steering was the most surprising difference upon first drive. It is much lighter in the F15. I think I'm going to get used to it just fine; it certainly wasn't a turn-off.
Speaking of turn-offs, this will be my first car with an idle engine shut down. Most people I know have it disabled or turn the feature off every time they get in the car. I didn't find the F15s to be that annoying. However, diesel might make that slightly different.
Oh yeah, and one last thing that makes the F15 faaaaar superior to the E70: sunglasses compartment
jk