My current GPS is a Garmin GPSMAP 76CS. But over the years I've also had a Garmin GPS12, Garmin eTrex Legend, and a Garmin GPSMAP 76S.
I like Garmin a lot. You have to understand that Garmin has about 85% market share in handheld GPS's, and they have it for a reason. The other guys do OK, but with only a few exceptions Garmin is the better unit or the better value.
The next thing is that you'll have a choice between a mapping GPS and a non-mapping GPS. The non-mapping GPS's are OK, but they have no street or topo maps. You can see waypoints and your breadcrumb-like track, but that's it. Mapping GPS's are much better, but also more expensive. And if you get a mapping GPS you need to factor in the price of the maps into your purchase.
Between mapping GPS's, there are kinds that can do autorouting and those that can't. Autorouting GPS's can calculate a route for you (take a left at 84th, right on Simms, etc.). Non-autorouting GPS's can only route between waypoints that you've entered. For hiking or boating, non-autorouting is fine. For street navigation, autorouting is really nice.
A good place to go for all sorts of GPS information is gpsinformation.net. They have lots of reviews and technical info. Also, I've found that gpscity.com is a good place to buy one.