Abductee- you work around those problems by taking them into consideration prior to the ride. Just like you would take a mapcase, learn how to use a compass properly, learn how to use catch features and other appropriate methods if you were navigating traditionally.
So you take a spare set of hig power batteries, look at the screen in the shade and carry the unit in your pocket. It's hardly rocket- science. Although I suppose the technology to put the GPS satellites into position IS rocket science, quite literally.
Hora- FWIW I've just traded in my old eTrex legend for null[url=http://www.memory-map.co.uk/road_angel_adventurer_satnav.htm]this[/url], A Roadangel Adventurer 7000. I already have a lot of Memorymap coverage so I was getting a bit fed up with not being able to use it when I was out and about. The £50 trade in suited me just fine as my Garmin eTrex was getting a bit tempremental to put it mildly but it has had seven years of hard use.
How about you buy/ obtain the cheapest possible working GPS unit and then use it to then get the £50 discount? Ebay is your friend