I believe investing in a gps with an Electronic Compass and Barometric Altimeter is very dependent on the user. Many gps users do not spend the time and effort to obtain the skills to successfully use a basic gps. While it is not difficult there is a learning curve. When you add the electronic compass and the altimeter you add two items that require calibration. I suggest that you download the manual at
http://www8.garmin.com/manuals/eTrexVistaCx_OwnersManual.pdf and see if you will calibrate them so that you can take full advantage of your purchase.
The pay back is not there for me. I carry a standard magnetic compass in my hunting gear, and it is not dependent on batteries. I would carry the magnetic compass even if my gps had an electronic compass.
I have Topo software loaded in my gps, and I carry topographic map in my daypack so I feel comfortable with the altitude information I get from them plus the satellite altitude reading from my gps. The barometric altimeter should be calibration daily.
In my world the two items are nice to have but are not a necessity. My hunting activity is normally between 2000-foot elevation and 8000-foot elevation. I believe that I could make use of the electronic compass, but again it is not a necessity. The average gps user can stop and look at his satellite compass and say I am going East, to my right is South.
A friend purchased a 60CSx last summer; he recently told me that he does not trust the Barometric Altimeter. I believe this is a case of not calibrating it on a daily bases.