I just finished a trek to south Georgia where I helped various law enforcement agencies with search warrants and arrests.
I used Microsoft Streets and Trips 2010 loaded on an Acer Nav 50 with Windows 7 Starter. The antenna was the standard antenna supplied by Microsoft. (The software was loaded by copying the DVD to a flash drive.)
The vehicle involved was a mobile command post. It is a flat-nosed 40' bus configuration with the front windows almost perpendicular to the ground. The only practical place to locate the antenna was on the dash abutting the windshield and the most available satellites were those only in front of the bus, however, the SiRF technology probably allowed some data to filter down through the aluminum roof.
The system performed flawlessly! There were never any "glitches" or computer hang-ups. Both original routes and re-routes were calculated quickly. The computer's battery was more than enough to operate both the computer and the antenna for several hours. The program was run for as long as 6 hours at a time and the battery was never depleted. I don't know what the total life would have been.
For those wondering whether Streets & Trips will work properly on the smaller computers, I would have to give a resounding "yes," at least on the Acer.
(Incidentally, the incident involved a dogfighting operation with participants from four states and stakes well into five figures. At least eight federal, state, county and local agencies were involved.)