I've been using a GPS for 6 or 7 years and have gone thru several. I have stuck with Garmin for 1 specific reason: They have several models (mine is a 12XL) that have audible alarms. Combine that with what they call 'proximity waypoints" and you have something very useful.

Audible alarm (you cna globally turn it off if you want) is pretty self explanatory - it makes a noise as you near a waypoint. The proximity thig is a bit different.

Normally the only notice you get when approaching a waypoint (you prviously set as a GOTO or part of a route) is a message on your screen. If you want to spend all day watching the screen, you'll see it. If you have the unit in your shirt pocket, you can hear the audible alarm.

A Porximity waypoint is also something you 'preset' but it does not have to be a GOTO or part of a route. ANYTIME you get within a predetermined distance from it, your (hopefully audible) alarm goes off.

Ideas for proximity waypoints: rapids, potential campsites along a river, shoals, quicksand, you get the idea.

BTW, I have found the 12XL to be relatively unaffected by tree cover, I always have it in a waterproof bag while yakking. A friend has an Etrex and has come to envy the audible alarm. Don't know why they don't all have them.