Deafbug is a great resource for the Minnesota TDI community! On Saturday, he helped me (well, he basically did everything- I held the light) install new rear rotors and pads. We also troubleshot my poor performace as of late- turned out to be a broken arm operator on the shudder-relief valve. Deafbug saved me $250 by macguyvering a repair to the plastic arm. That little fix has returned my car to it's old power curve (with the broken arm, my engine wimped out around 3000x).
Like Steve-O, I too have had my VW winter front on since late October. It really does make the car warm up faster (especially when the fan is on 0). The heat becomes too hot to keep the setting in red- so like Steve-O, I end up turning it down into the blue range. I mainly put it on because at my job I do a lot of short runs with extended stops- so I wanted to warm up my engine faster. But, as far as I can tell, the air intake is completely covered up when it's installed (up and to the left of the drivers headlight). We changed out my air filter and snowscreen and I noticed some seeds/debris in the snowscreen (no surprise) but there was quite a bit of large grass stems/seeds/debris that made it into my air filter. I was worried about whether the demand for air was met by opening the "trap door" in the snowscreen. I don't know how large blades of grass could have made it into my airfilter without coming through the trap door- so I took the top two parts of my winter front off (the 3rd piece is still installed on the bottom grill). I think I'll go with the water heater pipe insulation that others have installed in their grills.
Anyway, just wanted to let everyone know about Deafbug's great work. He doesn't do every repair but every repair he does well.
. But after filling up on ULSD for a few months now, my perception is that my mileage hasn't changed. 
