I had a Montana for about 4 years and could use it pretty well. Like most Garmin products, I found it over-priced and with a horrible user interface, but it worked well enough so I lived with the cost and aggravation. I lost the Montana a couple of weeks ago from its' rugged mount for the first time ever, even though I was habitual in making sure the mount clamped tight.
I've replaced it with a well used Samsung Galaxy S5 that is used exclusively offline. I was going to trade the S5 in for a $54 credit when I upgraded to the S7, so basically I got an Android GPS with a bigger screen for that price. The bike has a RAM Cross-Mount to hold it, and while the Cross mount has never given an issue, it now has a velcro strap as back-up. It's not perfect, as I need to run it on the internal battery in rain and in direct sunlight it could use a shade, so I just hold my hand over it when I need to. Whoopee. Those have been my biggest issues so far.
I got the S5 when they came out a couple of years ago and since last summer have been playing with different offline software. Like Bryce I ended up with OSMand+ and in one of the display modes, it is very high resolution. I find while I can re-size or move the display with one finger using buttons like a Garmin, the touch screen face to interface for everything else is MUCH MUCH faster and more intuitive. It will play music, podcasts, and even hotspot from the S7 if I want to see weather. I can adjust almost anything the way that I want it, not how a committee at Garmin tells me to do it.
So the bottom line is F* Garmin with their Holier-than-thou customer service, miserable interface, Base Camp, and extortion prices. They haven't kept up and like others, I have no intention of going back.