I'm interested to see that people are still buying dedicated Garmin units.
I have an Android phone, and use software (app) called Bike Computer Pro from a German company which cost a few pounds. It lets me follow tracks (usually created on Bikely/ Bike Radar and transferred as GPX) There are a number of map options including offline openstreetmaps. The only issue is battery life with the screen locked on, which is about 3 hours, so I now have a small USB pack which takes it up to 15 hours.
It probably isn't everything the Garmin is, but even if I'd bought phone and software just for this it would have been £300 cheaper than buying a Garmin unit (which I was thinking of doing).
I'm amazed at what the smartphone can do. I'd concede that it's not quite as good as the Garmin SatNav I use in the car, but I certainly wouldn't replace the dedicated Satnav if it failed. Same goes for a load of other things including cameras, ebooks, and more.