I did the switch from a 60cx to a Montana 600 a couple of months ago. The Montana works pretty much as advertised. The big push for me was the brighter screen and indeed I can read the screen in virtually all lighting conditions now.
It is nice having all the track memory I need.
If you get one you, need to be really cautious about upgrading the firmware. It seems like about every other revision causes more problems than it fixes.
I am about 4 revs behind and have no intention of upgrading until some feature comes along that I can't live without - like maybe not drawing a straight line between locations in the current track when you turn the unit off move to a new place and then turn it back on.
I took the Montana on a very rugged ride in Utah last month with no problems. I also only use it for off hiway motorcycle riding.
The Montana does not work as well with Mapsource as the 60. So I normally read and write to it from BaseCamp using files I created in Mapsource and transferring new files to Mapsource.
The Montana has lots more "features" than the 60 and it takes a while to learn them especially as noted above about maintaining and archiving tracks.
All in all it cost a little more than I would have liked to pay, but I am pretty happy with it.