A few things to note.. the current generation Golf/Jetta came out way back in 1999. The new one is due some time this fall as a 2006 model, and it should be an improvement over the then 8-year old design of the current Jetta.

Also, ULSD (ultra-low sulpher diesel) phases in sometime in mid 2006 and entirely nationwide some time in 2007. Once that's complete it will make all diesels a lot cleaner and make additional particulate traps possible on newly released diesel models.

Honda's i-CTDi diesel that they sell in Europe in the Civic and Accord is largely regarded as one of the best passenger car diesel engines ever developed. It's also very clean. Once the US has clean diesel fuel, we may finally see the i-CTDi's sold here. Also, you can run biodiesel in any diesel car with no modifications and that will also clean it up greatly.

I've driven the Golf 1.8T, which is their gas-based small turbo car and I thought it was quite nice. Although only rated at something like 24/31 with the manual transmission, I drove one from North Carolina to Arizona (2250 miles) and got 33-34.5mpg the whole way. I've read that TDi owners will often get over 50mpg at regular high interstate speeds and high 50's to 60mpg on lower speed secondary highways. That's quite impressive given there's no special aero tricks to the Golf/Jetta TDi and they weigh over 3000 pounds. I might take one for a test drive when the new generation comes out in the fall.