The new Etrex series GPS's are a great choice if you are looking for a GPS to take backpacking.
I chose the Etrex 20 because the only difference between the 20 and 30 are the altimeter, electronic compass and the ability to beam data to another GPS. I wouldn't use these extra features (I've had the compass and altimeter in the past and didn't use them) so the extra cost wasn't worth it for me.
I've had many GPS's in the past and am pretty critical of GPS features in general but the new Etrex 20 (and 30) have added a ton of feature that have made me very happy with the new units. The improvements that are important to me are the increased track storage (200 tracks... finally!!), 2000 waypoints, Birdseye imagery (downloading more as we speak... it does take time but I've downloaded 10 Gb so far... :), and the custom map support is great (I've loaded a few local park maps onto my GPS and they have detailed trails and landmarks on the map... very cool to be able to geo-reference your own maps!).
I don't use the GLONASS satellites as I think it degraded the accuracy in my area but tough to tell really... just might have been a bad sky day. Nice to have the option though.