I bought a Garmin HCx for backpacking but decided to load it with city maps and use on my 4 week bike tour this summer.
My initial plan was to run it the entire time I was riding using the routing and tracking features. After using up 2 sets of alkaline batteries in less than a week I decided ‘always on’ was wasteful. You do get tracks of where you are for every minute of your ride but realistically that’s too much information. As far as routing is concerned if all you’re doing is following a road it’s also overkill.
I ended up turning it off most of time and only using it when I was riding more complex (turn-wise) sections of my tour. I also did use it to save some “track points” for places I camped and picture locations. A set of batteries lasted for almost three weeks in this mode.
Obviously it’s fantastic if you’re at all confused about where you are, however it’s poor at giving you the “big” picture of your location. Paper maps and Google maps are still superior in this respect. Although it’s possible to eliminate paper maps I prefer to have both.
The Garmin HCx is an excellent device that does work as advertised, however (IMHO) the user interface is horribly designed.
I recently got the new iPhone and was hoping it would be usable as a touring GPS along with Camera/Phone/Emailer. Unfortunately the GPS is useless when you’re not near enough to cell towers. Plus the battery life is SHORT, although the interface is KING.