I got the TDI for 2 reasons: First and foremost was for the mileage, as my .:R32 was just killing us on fuel costs for the amount I drive (If my commute was shorter I would never have gotten rid of the .:R); but second was because I needed something with excellent fuel economy, but I couldn't stand to suffer through 4+ hours a day in an appliance...
The TDI is still fun to drive; not quite a GTI and definitely not an .:R, but torquey and enjoyable to toss into corners still at least, and I still get ~41-42 mpg on my commute even though I push it... alot...