I use a 76csx. I wrote a review in the first forum listed. The write may be searched ?
The Montana's touch screen turns off ? A touch system may not work in the damp or be un-functional in a dry bag. Is expensive for a lose able unit.
Garmin with the download picture op is use able for shallow tidal water.
The 76's screen is adequate and 7 years old. I'm typing on a new Inspiron with a much brighter screen than my 2006 Inspiron.
Kayakers without GPS want one.
The GPS is best used inside a dry bag attached to spray skirt. Wipe unit's holes with isopropyl then stretch 3M electrical tape over seams and ports. That's water resistant.
Fresh batts should last the day. Figure 2 batts every full summer's day.
See if you can search the review. Great fun.
You may wait till after Xmass for February panic sales...ask REI if REI plans to stock the 78...but even a 10% discount...$300 a price.