Hi,
First, being an old paper map and compass retro-grouch, it was not easy to make the switch, until reasonable function/cost mapping GPS units came along.
Haven't use a bike-specific GPS. However the older 60/62 Csx or Etrex units which allow maps to be plugged in or changed on micro SD chips have worked well for many years, and are available rather cheaply now esp used. They work well with 2 rechargeable NI-MH batteries, or can run longer on 2 lithium AA batteries. Of course, once on track, you can just turn it off and track miles on your bike computer until a turn or location question comes up. Some attach them to the bars. I just have a case for the GPs velcroed to my pack strap.
Haven't had a warranty problem, but these electronics usually have few failures after a year of use. A screen protector is worthwhile.
One problem is seeing the screen, given older eyes. You can now get sunglasses with reading lenses in the bottom which make maps and GPS screens much more readable. I just got a pair of these poly carbonate safety glasses for riding in dark conditions:
http://www.fullsource.com/bifocal-safety-glasses/uvex-s3765/I would not buy Garmin's maps, which are a clever way of selling our own USGS maps back to us.
I usually compile USGS 1:24k topo maps from a few states like CO/AZ/UT/NM/WY along with transparent trails overlays from Southwest Trails or My Trails on one SD chip. This is much faster if you write directly to the SD chip-versus using a cable to the GPS with chip installed. Writing a map will overwrite whatever map was on the chip in the "Garmin" folder! You can also save or copy this Gmapsupp.img file to other chips.
With these, you're covered in all those states, with a thumbnail sized chip. Of course, it is good to have an overall larger-(numerical) scale paper map along also. These GPS maps can be located at gpsfiledepot.com and downloaded. The site has info/help forums also. The Transparent trails overlays are a compilation and cataloging effort, using trail/track data from many sources and users. These maps/trails are a worthy effort, and many help by donating to cover expenses and a bit of beer $.
This takes a bit of practice first time, but produces good maps. I believe that Scott Morris, a map guru/computer science guy and an author of Topofusion has assembled maps covering GDMBR on his site. Also, give Topofusion a good look. A Demo version can be downloaded to evaluate.
Another reason to use GPS is the availability of tracks to be downloaded for newer rides or new trails. This can be a big help in unfamiliar areas, which may have many confusing trail intersections.
More recently, smart phone users are using their phones instead of a dedicated GPS.
Hope this gives some ideas.
Cheers,
Jay
