New firmware versions beyond 3.33

I also understand the check-in messages to be non-changeable as described here:https://support.garmin.com/en-US/?faq=y6jQ78qAaW6EvPvztACfj8

I suppose the only pro of switching from Preset to Check-in messages is that you can modify who received these via the messenger app vs. the internet explore page.

As the device sends only a code 1,2 or 3 via satellite to Garmin to decode Preset (or Check-in) messages I suppose without internet connection it would be impossible to change Preset messages in the Messenger app. This could result in a mismatch between actual and presumed text sent. To simplify things now the Check-in message is non changeable. Or you assume Garmin for trying to make more money as custom messages will now all go against the paid plan. 

I assume "BLE battery service" means that the battery level is now transmitted via Bluetooth. The new Messenger App now displays battery level of the device.

From the device end, check-ins replace preset messages. They are sent in the same way, from the same places, as presets were sent (before the change).

Message text, which is not editable:

"I'm checking in. Everything is OK."

"I'm starting my trip."

"I'm ending my trip.".

As with preset messages, you do NOT choose recipients on the device when sending. Recipients are set at explore.garmin.com. The Messages tab at explore.garmin.com makes it appear as if you can set separate recipients for each message. However, when you edit one of the messages, the recipient list is propagated to ALL messages.

Bottom line: Text is not editable. The recipient list is the same for all three messages. Check-in messages are not chargeable on any US plan.

Yes, I have verified that. We can see the battery %. I also see that with the Messenger app you can change all the device settings, start navigation (with or without sending points via satellite), etc... great, it's more comfortable that way.

What I haven't seen is the "Check-in" option. I think I saw it the other day when I looked at options after upgrading to 3.33, but now I don't see it (maybe almost better not even see it, hehe).

Another thing I see is that the "Messages" option in Garmin Explore now opens the Messenger app and also messages are sent instantly via land coverage if there is one. There are many new things around here and it's time to investigate

I see that a new option has appeared in Garmin Explore: "Delegate To Messenger", which can be turned on or off. I also see the device configuration options from Garmin Explore (v.3.5). From what I interpret, then Messenger is not necessary, but I see that it is still interesting because it requires one less touch to send a default message that I use a lot and that sends Mapshare "been here" (like tracking points, but free)

This integration with cell and WiFi coverage is one of the core features of the Messenger device, the associated Messenger app, and any other devices (such as the M2) which might eventually be usable with the Messenger app. 

I just finished installing 3.33 and the Messenger app. As Twolpert said… yet another app.  

After instaling it changed language to hungarian....IT wasn`t funny. Also pairing with Messenger app didn`t work. I had to reinstal the app.

I have been using the messenger app for 3 days. Garmin has an incredible chaos in it (probably like in everything). Preset messages (sent to 5 contacts) were displayed in duplicate and in the message details it was one message with mapshare and the other without Mapshare, plus the given messages were also displayed in private chats with individual people. The application was uninstalled, the account was unlinked to the messenger and I'm back to the good old SMS. Maybe Garmin will fix this sometime.

I do not understand all your motivation for installing the Messenger app. I prefer to have two separate channels for communication.

When outside mobile coverage I use inReach Mini 2 with Explore app.

When having mobile cell signal or WiFi, I use various apps on my iPhone.

Why make it more complicated?