I'm new to the area I'm hunting, so I wanted something with aerial, satellite, and more importantly , USGS maps at 1:24000. that pretty much narrowed it down to Bushnell or DeLorme. I looked at them both, and really didn't like Bushnell's usability (button layout). I loved the DeLorme.
The TOPO USA software it uses is nice. Obviously, DeLorme is a leader in maps and uses it's own software. It's also included, where many other models make you buy maps separately. This puts the price more in line with other units. You also get 100 bucks worth of free USGS, aerial, and satellite downloads. That comes out to about 400 square kms. Their customer service is great as well. I bought my unit a few months before the new software came out, so they sent it to me free of charge when it came out, and included another 100 dollars worth of downloads. I had trouble with my rechargeable battery, also, so they sent me a new battery, home, AND car charger. No questions asked. I just needed the battery.
So, overall I love the unit. It's user friendly, even for a tech retard like myself. It was easy to figure out, which is great since I only read directions after I break something. The maps are easy to cut and past as well. I've never used the SD card, since the onboard memory has more than enough room for everything I need. I have it in case I need it, though. Routes, waypoints, and tracking is awesome. When I was scouting my new area, I was able to mark potential stand sites, other hunters' stands, and areas of interest. You can add notes to them, and the key input system is very easy to use. When you transfer them back to your software on the computer, you can expand upon it even more. OR, you can plan your route on your computer, then transfer it to your unit. It really is easy to use.
It includes tides, sunset/sunrise for your location, and hunting/fishing high activity times, which is great in case you forget to look before you leave (which sometimes do). You can also map distance in the field. This has been very helpful to me, since it's a new area to hunt in. I can the distance from my current location (or other locations) to places shown on the USGS (or other) map. The other day I found a great place to put a stand (my area in Massachusetts is very congested). I could check the distance from my location to a house shown on the map to make sure I was 500 feet away. Without the DeLorme, I wouldn't have even known it was there.
The only thing I wish it had was a magnetic compass, but I carry one anyway. Even that isn't such a big deal, since the GPS is so sensitive. If I take 2 or 3 steps in a direction, it marks my travel direction and corrects the compass.
If you have more specific questions, feel free to ask.