In July 2012, I bought a Garmin GPSMAP 62s, the newer version of the 60. It is a huge step up! I added a 16gb memory card and maps as well.
First of all, this one has a triaxial compass. Like the 60, when you are moving (faster than 10fps), it determines your direction from the satellites, but when you are going slower (walking), the electronic compass takes over. With the 60, you had to hold it flat and level and it did pretty good. With the 62, you can hold it at any angle.
This one also cycles up and calculates routes much faster. This one comes on, calculates a full route in a matter of seconds, whereas the 60 might take up to 4-5 minutes from a cold start.
You can also add topo maps, tell it to route through the area trying to keep at the same elevation. With the right types of maps, it can also route along a trail.
It calculates sunrise, sunset, times till each and adjusts these based on your current location.
Geocahcing is much easier with this one as well. You can download the full cache description and hints to the GPS.
The accuracy of the 62 is a step up from the 60. When caching, the 60 did very well, even in heavy cover, getting me to within 20 feet of the cache. The 62 gets me right on top of the cache, almost always within 5 feet, even in heavy cover, trees. The accuracy of the 62 is also noticeably better in rain and overcast skys.
Both are waterproof. Garmin makes a couple of models with touchscreens, but I decided against those. When you are using it with gloves (or cold hands), the touch screens are a bit more tricky, where as the buttons on the 62 seem to work better for me.