There is nothing "simple" about the Garmin Tread navigators...and Garmin designed them that way. As you say, when in the outback, why bring internet - or cell service with you?
I - and one of my overlanding buddies - both bought a Garmin Tread Overlander with the built-in InReach. Mine is an 8", my buddy bought the 10". Both of us are long-time Garmin GPS users and have several of them, various models. We both agree on the following pluses:
1) The screens are marvelous. Very bright, very sharp and clear. My old eyes LOVE the screen.
2) The included maps are the best Garmin has ever put on a GPS unit. For once most trails and two-tracks and MVUMs show up on the screen.
The minuses are many!
1) Having the vehicle speed as one of four fields on the map page - and that can't be changed. Why would anyone poking along on a trail care what speed they are traveling? The vehicle's speedometer isn't good enough?
2) The heading can only show West, North, South, etc. Can't specify degrees of heading the way you can on any of the handheld GPS units. Degrees of heading is essential to anyone working Search and Rescue.
Degrees heading on a Garmin Montana. Can't have this on a Tread!
3) By far the most egregious thing about the Tread series is that they are designed to work paired with a smart phone. And using Garmin's "Tread" app - and through Garmin's "cloud". It tells you that right in the owners manual. Apparently Garmin engineers never travel where there is no cell signal. The Tread won't work the way the older Garmin units did - create a track or other GPX file on a laptop or tablet or whatever, connect the GPS unit to the laptop via USB and transfer the GPX file to the GPS unit. You can use a Tread with no cell signal available - but you have to make sure you have all the GPX data loaded while you are in cell range. There is a workaround - you can create a GPX file on a laptop or other device, load that onto a microSD card, insert that card into the Tread, and import it. The Tread WILL NOT work with Garmin's Basecamp or most other GPS apps. And here's the worst part - when I first downloaded the Tread app onto my smart phone it worked just like it was supposed to once I "paired" the phone and the Tread. That lasted less than a month. Now, the phone and the Tread still pair - if I'm in cell range I still get weather, etc., from the phone. But the Tread app on the phone refuses to share data with the Tread GPS unit so none of the GPX data that is on the "cloud" will transfer to the Tread GPS. And from what I read on line, we are not the only ones having this Tread app - Tread GPS data sharing problem.
The Tread would be an excellent GPS unit if it worked like the older Garmin Montana units...send and receive GPX data via a USB cord or "share wirelessly". Create a waypoint or track on the GPS unit, name it, and save it into a folder so that it is easily accessible for future use. No, Garmin had to complicate matters and try to make everything work through Bluetooth and the "cloud".
But the Tread screen and maps are excellent:
