I have an '06 Jetta TDI 5 speed Manual Transmission. Reports are correct of highway mileage of 50+ . They are obtainable .

• In 5th gear cruising at 58 mph, I get 52 mpg. This is the sweet spot for the manual. Granted I usually drive faster than that.
• The automatic has 6 gears and will slightly beat the manual at speeds greater than 58 mph.
• Between 60 and 70 mph gas mileage drops down to about 48 mph.
• 70 to 80 mph mileage is about 46 mpg.
• Stop and go traffic mileage sucks just like any other car except a hybrid.
• Around the city I usually average 38 mpg.
• The TDI has plenty of power and is fun to drive.
• A diesel engine is louder than gas. Can't tell unless you have the windows down.

A hybrid might be a better choice if you drive short distance mostly in the city. If you drive more than 50% of the time over 40 mph without a lot of starting and stopping, I would recommend the diesel TDI. Diesel engines have a proven track record as compared to hybrids. My combined mileage from the day I bought the car is 44.8 mpg. I know that I could do a lttle better but that wouldn't be as much fun.

P.S. I am not selling my car, I just thought I would let everyone know about my experience.  By the way the new Jetta diesel TDI's won't be available until late fall of 2008 as a 2009 model year.