I've only had my '11 335d for about two weeks, but I'm already in love with it. Power for DAYS, and I still get 27-28mpg city and 41mpg highway (at 80mph) when I keep my foot out of it. Shortly after I got it, I had to take it in for a recall (emissions stuff), and got a 2011 328xi as a loaner. I was actually amazed that it was noisier than the d, and it also felt much slower in normal driving than the 2000 323i I traded in.
Get the diesel. It's just an amazing car. So much so that I barely miss my manual trans. I do miss it, but not as much as I feared.