Go see one in a store, and try navigating in demo mode before you plunk down the bucks. The screen is too tiny to be used as a CP. If you zoom out beyond a 1/4 or maybe 1/2 mile radius you won't have sufficient detail for navigation and the map will be of very limited value. See if you can grab a GPSMAP 478 left-over, or consider the new 620, you'll be much happier with the usability.

If not, all you need is a GPS position and you'll still need to reference a paper chart so consider going for a more basic handheld and save your money.