What you haven't said is what you want to use the GPS for. Snag hit on this already. You have to ask how it will help you and what you want it to do. I have used GPS for years, especially for work, but haven't used it for hunting, though I'm a pretty new hunter. Here's some food for thought.
If you are looking at topo maps, either paper or electronic, and you see a spot that you want to walk in to and scout, you can enter the coordinates of the location as a way point and walk to it using the GPS.
If you are out hunting or scouting and find a spot you want to return to, you can log it as a way point, and then walk back to it the next day, week etc.
If you hunting an unfamiliar piece of land and want to make sure you can find your way home, you can mark your vehicle as a way point and then navigate back to it.
Until recently, a weakness of any GPS was its inability to pick up satellites under dense tree canopy or in valleys. Its a real pain to have GPS stop working due to loss of signal. The new high sensitivity antenas have largely done away with this.
It sounds goofy, but remember a GPS works on batteries. Always carry extra, even if you just put fresh ones in. In cold weather they go much faster. If you keep the GPS in an inner layer this helps, but that means it is turned off and you won't have a track log for everywhere you've gone and you have to wait for it to aquire satellites before you use it.
Also, check out the buttons and display screen. The Garmin etrex series works well, but the screen and buttons are small. My next GPS will have a bigger screen.
I also think it is a good idea to know how to navigate with a commpass and a map. It gives you an understanding of what a GPS does for you, and a compass doesn't need batteries.
You can also email GPS files of your favorite hunting spots to friends....Ok so maybe that doesn't happen too often !!!
All that said, even the basic GPS models out there have more than adequate features for hunters. I would tend to go with a brand/model that you find easy to use. If you have friends that have GPS - try theirs out.