The Garmin e-trex Legend (reviewed earlier here ) is still the best GPS unit per pound. It is small and light. I continue to use mine for mountaineering when I want to log a trip while carrying the absolute least amount of weight.
Recently however Garmin has come out with a host of new large color screen models with unbelievable battery efficiency. The GPSmap 60C and 76C have nice large color screens, faster satellite acquisition, much improved button and software interfaces, and these will run for 30 hours on a set of AA batteries. While the e-trex can load in topo maps just like the 60c can, it lacks color, and a color screen is really the only way to look at complex data — such as a topo map — on a hand held. I have used my 60C all summer on a host of mountain biking, hiking, climbing, and driving trips and consider it well worth the $350 (street price) price tag.
(Note: The “CS” versions of the 60C and 76C have an electronic compass and barometer, as well as some extra software features around glide path and vertical speed etc. These extra functions cost extra money and eek out 30% less battery life when activated making them not worth it to me.)
So while the 60C is significantly larger, which makes it tougher to wear, and a bit heavier, the added functionality and especially battery life have made it the one I use almost exclusively. If you are going to buy one GPS unit, the Garmin 60c is the one to get.
[Extra Tip: Make sure you update the "firmware" in your GPS and the CD-Rom software periodically on the Garmin Website. They are always making improvements to the internal software and PC interface and its well worth the trouble of updating. ]