Im not an expert on gps I've only owned 2 of them. 1 was the Rhino 120 with a radio and the other is a Garmin Oregon 450T and the Oregon is a lot better than the Rhino 120 ...bigger screen, sd card slot for maps, touch screen which IMHO is the only way to go. I am really happy with the Oregon 450T it was really easy to learn how to use it. As far as batterys I found if I use Lithieum batterys thay seem to last about 3 or 4 times longer...same goes for my camera, that thing would eat batterys now with the Lithieum they last for weeks at a time.
ps... From what I've been reading the Montana gps with the camera would really be nice because you can take a pic on the run and make it a waypoint....you wouldn't have to type in a name or location. Like if you were riding a horse or atv. Just take a pic and put a name on it later.....sounds good anyway.