It's six weeks now since I started using an eTrex 20, so I thought I'ld share my experience with you.
WITH WHAT DO I COMPARE?
This is my third satnav in the eTrex series: my first was an eTrex Legend H (it's display died), then an eTrex Legend HCx (still working but it's accuracy suffers badly, completely my own fault), and now I went for the eTrex 20. Here-below are a few conclusions, after having used it more or less "seriously". Please note that these are just my own personal findings, they are not the results of extensive lab-tests.
THE GOOD.
1) Speed of location fix as well as accuracy are (very) good. I should mention that I have enabled GPS and GLONASS satellite reception, as well as WAAS.
2) Display quality is fair in sunlight to good otherwise.
3) Speed of processing: from time to time you notice that the device has only just enough, or maybe just not enough cpu power. For example when redrawing the map, or when handling stored tracks. But you have control over this, by enabling only the map(s) that you need, by storing only the track(s) that you need, and by setting the level of map detail to display.
THE BAD.
4) Handling capability of the device is not good.
4a) Garmin moved the joystick to the top-right corner of the frontpanel - which is really the worst place, when you handle your satnav with your left hand (which I always do).
4b) The mounting system does not allow you to detach nor re-attach the device with a single hand. Unless you are sleight of hand, maybe.
5) The build quality feels a lot less robust as that of the older eTrex models. Concrete examples:
5a) It is really easy to close the battery lid "in a wrong way", almost certainly leaving the unit all but watertight (but as you can imagine, I have not checked this).
5b) The locking mechanism of the battery compartment: you would expect it on a toy, not on an outdoor device.
5c) The slot holding the microSD card is just too fragile, compared to where it is located (underneath the batteries). I am not that clumsy, but when changing batteries I have to be really careful not to open the slot holding the microSD card accidently -- when your hands are cold, I bet you might have trouble.
THE UGLY.
6) When you want to use GPX files on your device, you'ld better be sure that your GPX files are written "the Garmin way". Just writing well-formed GPX files is not enough: GPX files which work perfectly well for any (other) app may still go wrong on the eTrex 20. Worse, they might confuse the device and make it misbehave. If you can prepare your GPX files well in advance, using the "correct" tools, that is not a problem. However, when you are in some sort of emergency situation and cannot choose everything you'ld like to, this might make the device miss its goal altogether...