The batteries died 3x within one hike (10hrs rt of Humphrey's in AZ). The conditions were above freezing, without strong wind, and the GPS was stored inside our pack. Then at the summit, the GPS displayed we were more than 200ft higher than record for the mountain. Not worth it for the high cost in my opinion.
I bought this in spite of the bad reviews because I wanted custom maps. And, with some work, I did get some mountain biking maps loaded. It's a finicky process, though. I recommend searching for a Garmin support page called "General Guidelines for Creating Garmin Custom Maps" to learn about some of the gotchas before you sink time into this.