It uses 20 channel SiRFstarIII technology.
Here's the full spec:
http://www.miogps.com/US/products_c310xspecs.htm
If you go to Circuit City's website, a lot of the reviews are good. 4.2 out of 5.0 according to 454 users. I've had mine for a month now and would definitely recommend it. It's not as good as the OEM NavTeq in my Acura TL but definitely better than my Navman PiN570 PDA/GPS. It will definitely hold its own. You can't beat the price/value of $200 shipped.
Reviews:
http://www.gpslodge.com/archives/008669.php
http://www.circuitcity.com/ssm/Custo...Review.do#tabs