I used one in the Army for a year. It did an adequate jo; I could plug in coords, and, with the use of a map, was decent for its size. The downside was that I would lose signal alot. And, it takes AAA batts IIRC. This forces you to take two separate types of batts with you, or me anyway, as most other gear I carry takes AA.
I would second spending a little extra on an etre. With the availabilty of them these days, $100 will get you a great GPS, if you're lucky, you could even pick up a used one with a mapping feature.