I have been using an eTrex Summit for 8 years now and it still works fine, it's not mapping, but the magnetic compass works well. I can upload caches to it no problem with the Garmin cable and a Keyspan USB to Serial adaptor using the Garmin Plugin for the geocahcing website. (This option dosn't work on the Mac OS but there is a work around) Altough the limit of 6 charactors for waypoint names can be pain as some cache names GCxx... can be longer that 6.
I have recently upgraded to a Garmin Oregon 300, very much the same as the Colorado, but with a touch screen, which makes input and moving the map around much easier, and it's not actually that much more costly. The accuracy seems quite good, finds lots of satellites, much better than the eTrex, but the it is 8 years old. However I like the eTrex's magnetic compass better, the Oregon is slow to switch between GPS and compass and can be slow to update. But still stoked with the Oregon, paperless caching, street and topo maps. And you just plug it into USB (Mac or Windows) and it works fine.