As I am usually complaining about something
I thought I would take this chance to dis-complain
and add another data-point to the discussion.
The android app works well for me:
I run it on a 6P running standard Android 7.1.1
and on a rooted HTC M8 running Cyanogen 11- M12
and multiple Linux/ Kubuntu 14.04 machines.
I have 2 different configuration points to @totoba:
1. I always start it manually - not on bootup.
2. I don't try to sync external sd cards.
(I have given up on external sdcards on Android,
so many apps don't work with them).
3. I don't sync thousands of files, but I do sync hundreds.
Some directories are 4gb of 50-750mb map files.
That said, I don't really get any crashes
(or maybe so few that I don't notice them).
I do sometimes get high cpu and a hot phone
but that happens even without Syncthing running.
(Still can't find the cause).
Sometimes I do need to go into the web gui - but I don't really find it painful.
Maybe I'm just used to more pain that @Antony Male