Some time ago I purchased a Radio Shack GMRS (2 watt??). They don't age well, in other words, the performance dropped noticeably as they aged so I don't think I'd recommend RS. When the radios were new, my friend and I could keep in touch, all over large ski resorts like Sugar Bowl, Squaw or Alpine Meadows. If we got separated without the radios, the next time we'd meet up was lunch or in time to leave. That gives you an idea of the area they'll cover provided we weren't on opposite sides of the mountain.
As drzinc suggests, less power (any decent radio) will work for any line of sight outside job. Inside the bowels of a building is another story. That will be more of a YMMV (Your Milage May Vary) proposition. If you want to have this as a permanent part of your kit try to stick to one of the better known brands (Motorola, Cobra etc.)
I was not favorably impressed with the FRS band. Too many people bought them for their kids. The GMRS were intended for business use and required a license to legally operate them.
Does anyone know if that is still the case?