I started out Geocaching in 2005.
I used a Garmin Legend till late last year. I kept talking myself out of upgrading since the Legend still worked perfectly fine. Yes, a color screen would be nice and a more sensitive receiver and finally broke down after many months of debating.
I was looking into the Colorado and Oregon and found most liked the Oregon better the the Colorado for Geocaching. A nice feature with both units is that you can download the info into them about the caches you are searching for, "Paperless". Such as cache size, Description, Last logs by other finders, etc.
The Oregon cost more then I wanted to pay, plus the "Paperless" feature did not mean that much to me since I use a PPC for the cache info.
I ended up buying a Garmin GPSMAP 60CSx. I love this GPS.
Bought it new off ebay, shipped to my house for $270.00 which was a great deal when I purchased it. I just did a search and see I can find a new unit shipped for $281.00.
I would also recommend the TOPO maps to load into the GPS.

As for a used one.. not sure about that one. Maybe if it was a friends who was upgrading.