I've been using a Garmin GPSmap 60CSx for the last couple years. Its worked well and there has never been a situation that I haven't been able to get a signal, even in dense forest or canyons. I did buy a larger memory card and as you probably know you have to buy the software for specific maps or a memory chip that has it all preloaded. Its cheaper to buy a CD/DVD and load your own maps, but its more convenient to just buy the memory all ready to go. This particular GPS also supports marine maps. It has a nice large screen and color maps and lots more features than I'll ever need or use.
Let me start off by saying I am not a farmer.
I am a deer hunter and I do own a tractor and have all of the equipment - but that does not make you a farmer any more than standing in the garage makes you a car - well, you get the picture!
Having said that - and with most of my ineptitude fairly well hidden - I do think that buckwheat is one of the most under rated cover crops out there.
I say cover crop because I see mixed results as it relates to the deer eating the plants.