Since it is not time-dependent, you don't have to calculate in advance when you'll probably arrive and then set up an unreliable alarm. Up to now I had always done it this way and always had to add a lot of Buffer (it could be that the train is too early this time - which happens more often than you think). But most of the time the trains are too late and are delayed and then the alarm goes off much too early and you always set new alarm times again and this is totally crazy and it just works badly the old way.
The fact that I can wake up with out waking up my other two house mates is great. The watch taps me gently and increases until I start moving around, to which it then fades away and if I don't move again for a few minutes it comes back. It's a really gentle and effective way of nudging you awake without getting in the habit of hitting snooze.
The watch and app graphics are nice and dark. I point this out because too many sleep apps are way too bright.
I can start the alarm from my watch, my phone can be plugged in and away.
I would like to see some refinements in the app UI. There are a lot of great features but they're hidden behind strange buttons and tucked away deep within menus. A walk-through wizard to set up the alarm and an easy to update dashboard when you first get to the app would be amazing.