Warning!

If you haven't updated to firmware 3.9.x, I would hold off doing so for now. Two nights in a row since the update my watch has spontaneously deleted all applications and watchfaces from itself. Obviously that wouldn't matter too much if you were using Android / IOS, because they'd be reloaded as they're used, but on Sailfish it's a problem...

I'll try a factory reset and see if that gets me any further.

[edit - incidentally there also seem to be a few reports of terrible battery life on this version.]