I'm still enjoying the M1 itself without issue, it's become a member of the family (12hrs underwater last weekend & over 50 dives in last 3mth), but have a small niggling observation with logs and how their handled.
I noticed when syncing and downloading logs to the app it uses a lot of cell data (I don't have unlimited), I disabled data and was no longer able to sync my logs, it's cloudbased you basically need an active internet connection so I now only do it after a trip at home. I can't quickly sync and add notes between dives directly on the phone. Seems to view logs in the app they need to be downloaded to their server not just the app locally.. to me it would make more sense to sync M1 > app locally using just the BT, and upload data only if you want to share rather than forcing it or optionally later when wifi is present. Plus there is no opt-out for sharing your data onto their server, though you can set dives to private.
I don't really want to log on my phone via their app, just use it as a gateway to get the log data into subsurface as easily as possible.
To me this raises 3 potential issues, 1) if you happen to be on a liveaboard or remote location without internet connection you can't actually use their logging app to log any dive info or notes as you couldn't get the log out of the M1 in the first place; 2) if the company does ever go out of business you have no way to access your logs; 3) privacy concerns.
Of course at some point it would not be too hard for someone to sniff the protocol to access directly or have the libdivecomputer guys add support
