I've had my X5 35d for exactly one month today and will be writing up a report to post in a while. I'm at just over 1000 miles and 1/4 the way through the third tank of diesel, averaging 21+ MPG at 30 MPG average in mostly mixed commuting.

I enjoy the balance of the engine and transmission in the 35d, and I've learned how to use the DS and M modes if I really feel the need to get moving quickly. The only thing I'd like to see improved is the initial off-the-line acceleration. It's fine in most traffic, but it doesn't "leap" off the line like a gas engine can. From 5 or so MPH it starts to go like a freight train, and will often overtake cars that were quicker off the line.

I considered a 35i and liked the way that they felt on test drives, but the 35d had multiple advantages and incentives in its favor. The 50i was never really a consideration as the one that I test drove didn't feel significantly faster than the 35i in normal daily driving situations, and I knew that it would be awful in the economy department. I'm not really a "greenie" (despite living and working near the People's Republic of Boulder), but I don't mind not having to fill up so often, and I can wave the alternative fuel/clean emissions/etc. flag to shut the greenies up.