I have one.
Unfortunately at this time, for me at least nothing works notification wise. I got this knowing that extra features like the high five thing and such wouldn't work for WP but in their page FAQ it states: "...notifications beyond SMS currently do not work..." which I took as SMS notifications work but nothing else and I'm fine with that but I can't figure out how to make it work, if it does at all. Customer support is no help on the matter just doing the usual "It's only available for iOS or Android" not even knowing that there are apps for WP. I will give it a bit of leeway considering they call them beta apps in the same FAQ question. I will say the 'phone disconnected' notification works and has saved me from leaving my phone behind a couple times already this holiday season.
I also wanted more a watch than fitness tracker and for the most part the watch function works well. It can't stay on at all times though I'm not sure if it's a setting that not available so you have two options to view it; 1. Press the button to turn on the display, which for me trying to use it as a watch defeats the purpose or 2. Have the display turn on based on motion when your wrist is rotated which in my experience is pretty solid, the only problems being when laying down it doesn't always work flawless and it doesn't work when in sleep mode.
So at this point in time if your primary purpose is notifications, it's not there yet, though hopefully soon with 8.1 update 1 going out it won't be too long.