When it comes to GPS units, you can go from simple to wildly complex, so it's important to decide how much GPS you need. Much like computers, the capability you buy now will be eclipsed and obsolete next year.
I've used a Magellan Sport Trak Topo for the last several years. This is about a mid-level capability/cost unit. It's perfect for my needs, that of a GPS to mark hunting/stand locations, downed game, off road travel routes, and so on. The accuracy of the topographics is freaky, it even shows sloughs and prairie trails around my farmstead.
This is a great unit for outdoors use, but you probably want more capability if you intend to also use your unit for road navigation. The Sport Trak shows roads and does the job, but the function is fairly basic compared to stuff that's now available.
When out hunting in say, the Badlands, I power the GPS up, mark my starting point in the morning, cross reference that with a compass & map, then shut it down and put it away. To find my way back at the end of the day, I just power it up and hit the "Go To" button back to my marked starting point.
Going in when it's still dark, it works fantastic for following a pre-saved route to a stand.
Early Goose Season starts next weekend up here. In the next several days, I'll be marking spread locations in fields around my farmstead. Makes it a snap to go right to the exact spot in a several thousand acre stubble field I want to set up in before light.
It's literally the cat's rear end for, after killing a deer at last light in about half section of CRP, coming straight back to it with the game cart to bring it out in the dark.
Ever followed a blood trail in the dark, had to go get help/decide to stop and take it up in the morning? Just mark the location with you GPS and follow your back track right to it when you return.
These functions have saved me a world of work and headaches.
What ever unit you get, make sure it has 12 channels. 8 channels (if you can still even find one) were always cheaper, but tend to constantly lose the satellites. Mid- to upper level 12 channel units will hold the satellites even under tree cover.
Also, if you use it for hunting navigation, ALWAYS carry a couple extra sets of batteries and a compass in case it goes belly up...