They are illegal to use without an amateur radio license, even on FRS/GMRS frequencies.
On simplex, they're going to be slightly better than a standard FRS radio. A ~6" flexible antenna and the 5 watts of output will help things a bit. If you get an adapter, you can use a mag mount on the roof of your truck, which will improve things a great deal. You are pretty much limited to line of sight, but they will punch through vegetation/trees decently.
The batteries last me about a week of intermittent use. I'm not sure what practical way you would recharge them in the field. I'd just bring along multiple batteries. They're about $10 and pretty lightweight.
They're a much better radio than a bubble pack radio, but they are manufactured cheaper. They are pretty drop resistant, but I wouldn't expect them to handle a lot of water. You'd probably be better off with a Yaesu if you want something 100% reliable that you can drop in a creek.
I use them frequently for backpacking. We have a ton of repeaters around here, and they allow me to talk freely with friends/family while I'm in remote areas.