With a My Touch 4G through T-Mobile and I am impressed. What I like most about it is it is also a "Hotspot" so I can do away with my Sprint Wireless dongle. It is sized nearly identically to my iPhone and the voice recognition stuff seems to work quite well. Last night I pushed one button (the "genius" button) said the name of a restaurant and a moment later it starts navigating me there in a style reminiscent of a Garmin Nuvi.