If there's really no downside to the diesel driving experience, there certainly is an upside when you go to refuel. That is: You won't have to do it very often. The 335d's EPA rating of 23 mpg city spanks the 335i's 17 mpg rating, and the diesel's highway figure of 36 mpg beats the gasoline-powered car by an even more impressive 10 mpg. The range on a full tank can easily exceed 500 miles.
The price you pay for this blend of performance and parsimony is $3600. At least that's difference in the base sticker price of the 335d versus the 335i sedan. But it's actually a lot less. The 335i does not come with an automatic transmission, so add that and the gap narrows by $1325. Then there's the federal government, which wants to throw $900 at you (in the form a tax credit) for treating yourself to a new BMW diesel. So the actual extra outlay is more like $1375. But with the diesel likely to enjoy better resale value, the diesel premium probably is even less.
The 335d is the eco-friendly machine that doesn't just bolster your environmentalist cred, it flatters your intellect as well. Or it would, if other people could tell you're driving one. That little "d" on the trunk lid, though, is pretty hard to spot.