Very durable -- have even used diving and bright enough to see elapsed time if one uses as a stop watch.
To get any type of compass accuracy you need to reset the unit (manually spinning the watch slowly 360 degrees while in calibrate mode) to guard against any magnetization, and you'd pretty much want to do that prior to any trip; thus if you do a lot of trips you'd be doing this often, and I haven't tried, but I wouldn't want to use the compass for anything more than guidance as to a direction as opposed to say your GPS or handheld compass...
