It's quite interesting to hear that, on the Audi form I keep an eye on they all talk about this engine like it's the second coming. I've been thinking about changing my 2.0T for one as I do about 1500 miles a month, not sure I can bring myself to do it though.
Don't get a diesel unless you really need to because of mileage. They are annoying and the equivalent petrols are generally nicer. My 535d isn't bad, but then it's twice as powerful as a 2.0 TDI 170 and far more refined. I'd still have a 540i if it didn't get much worse fuel economy.