I use and Etrex Vista for my walking. It is a good, small and light, unit with many good features, including
1) Map screen
2) Electronic Compass
3) Barometer/Altimeter
One problem I would say is that is if you down load maps of national parks from MapSource then the screen is an unhelpful shade of grey that makes everything difficult to read.
Other than that excellent....I paid £300 for mine but they are on ebay for about £150. And the other (less speced models) are a lot cheaper too.
Flaps