The PC Miler GPS unit is pretty bad, and they should be taken out back and shot for calling it PC Miler when it doesn't even have PC Miler on it. It's an electronic version of Co-Pilot, which sux, not MC Miler, which doesn't.
Best bet for a standalone GPS unit is a mid-rage to high-end Garmin, with Tom Tom being a close second. Garmin has slightly better routing, but the differences are minimal. Mainly the differences are in the user interface - whichever one you use first, Garmin or Tom Tom, that's the one you'll like. The Garmin is actually better for North America, and the Tom Tom is better for Europe, but again, they are very, very close to each other as far as mapping and routing are concerned. Don't mess with any other brand of GPS, like Goodyear, Cobra, BillyJoeBob, as they all fall behind the Garmin and Tom Tom.
The ones for sale at truck stops tend to be lower end units. Get it online or at a Best Buy or something. The newest
Garmin nüvi 1690 is finally getting to where GPS units are heading, with the
nüLink!™ Services (not available in Canada, of course) that gives you real-time information delivered wirelessly about all kinds of things, including local fuel prices, Google Local Search, local event, weather and real-time traffic. And it's got all the kewl stuff like Bluetooth, lane assist with junction view, etc. It's also got a complete White Pages phone book. It's gnarly. Not truck specific, tho, as that's obviously still a work in progress, but it's still gnarly.