Some of you might be interested in this. I tested a Terratec dual-tuner DVB-stick up to 120km and it works well.
I used a UMPC (Via 1.2Ghz) as the PC and didn't really do much to optimised the positioning of the antenna. (antennas, antenni ? !!)
Up to about 60kmh its very stable in my city (Bonn, Germany) but with some re-positioning of the antenna inside the car I managed to get TV reception up to 120kmh.
While I was messing around, I also tested a UMPC mount on the sunroof. It needs soem sort of extra security fixing but it's a great position for rear passengers.
I wrote up an article and included a video at UMPCPortal. Feel free to ask questions here or there!
UMPC + DVB-T in-car Testing.
Regards
Chippy