I got my 2009 Jetta Sportwagen TDI "fixed" on 9/20, so it has been a little over a week. So far, I'm not very happy with the changes. Other than the sound, the car drives similarly: acceleration to 60 from stopped and acceleration at speed seems about the same.
Major issues: MPG, overwhelming diesel exhaust smell, visible gray exhaust smoke that wafts into the passenger compartment when idling in traffic unless there is a breeze in the right direction.
Prior to the fix, I was getting near 40 MPG on the MFI display on my morning commute and close to 36 MPG in the evening (more traffic, less time at highway speeds). Now I'm lucky if the morning gets to 30 MPG and in the evening, it has been as low as 22 MPG. My miles driving divided by estimated consumption (about 1/4 tank left) is in agreement with the above 25% reduction in fuel economy. This is very disappointing.
The exhaust issues are even worse. The smell is overwhelming when idling in traffic, unless there is a breeze to dissipate the smoke and odor. The only option is to close the windows, turn on the AC and press the recirculate button to isolate the interior.
The smell gets stronger and weaker, and is sometimes noticeable when driving at city speeds (25mph). I can't see the exhaust smoke in the rear view mirror when moving faster than about 10mph.
The dealer said there might be a smell during the first tank of fuel (still on first tank), due to lubricants and oils used when fixing the exhaust system. I'm willing to wait until after the first fill up to make my final judgment, but if the smell and smoke continue, I'd consider the "fix" completely inadequate. It's bad enough to give me a headache and make me and my children feel nauseous.
I also had a 2012 Jetta Sportwagen TDI, which I sold back to VW. If the exhaust issues can't be resolved, I'd like to get VW to buy back my '09, too.