The Personal Coverage Check is easy to use – just punch in an address, and you'll see a map with gradations of coverage from forest green (perfect) to ghostly white (none at all.) T-Mobile updates the PCC Web site weekly and ties it into their engineering systems for the most honest possible picture, the carrier says.

We tried the Personal Coverage Check with a dozen locations we know around the US, and it usually worked flawlessly. It only failed with one location: downtown Manhattan, where the Personal Coverage Check says T-Mobile has no weak spots. T-Mobile told us their system has trouble because "Manhattan is a unique environment," and that's true: building penetration issues, signal crowding and multipath reflections make the nation's densest neighborhoods a painful test for any wireless system.

We asked the other major carriers why they don't give consumers similar information. (Most carriers' maps just paint a wide swathe of coverage over an area, not going down to the block-by-block level or differentiating strong signals from weak ones.) Sprint and Verizon dodged the question; Cingular said they're planning to improve their own coverage maps soon.

We are truly impressed with T-Mobile and their PCC's honesty so much, we would name it a major reason to switch from less-revealing carriers to T-Mobile – as long as T-Mobile works where you need it. Thanks to this Web site, you can now easily find that out.