When using GMRS on FRS frequencies, you are only allowed to use channels 1 - 7, and only a maximum of 5 watts under those circumstances.
GMRS used to be popular with businesses, but the FCC has shifted it's direction to be more of a family radio system, similar to FRS, but with more power, and options such as repeaters. There are still some businesses that are grandfathered in, and can continue to use GMRS. New businesses can also use GMRS, but each employee using the radios needs to obtain their own personal license, so it's not an attractive option. It's not the kind of radio service where you can expect to get on the air, call CQ, and get several replies and talk radio all night. Odds are you're going to get some little kids, or some lawn maintenance guys. Don't count on it for any kind of emergency help.
Range varies due to terrain, etc. But typically radio to radio, about 1-5 miles, depending on power and antennas. If you go through a repeater, then again, depending on many variables, maybe 10-30 miles.
I think for most people, your just as well of with a couple good quality FRS radios, and no license fee.