Been sporting a Fitbit Surge since my third Band 2 died and was looking at these as an option compared to the Iconic they are releasing. I like the Garmin Connect interface on Mobile and Desktop. It actually leaves Windows Mobile off their specs sheet though (WM is listed on some devices).
https://buy.garmin.com/en-US/US/p/571520#specs
That was the only reason I didn't make the jump to Garmin though, as I much prefer the actual watch look to the miniature tile screen. Do you have Calendar notifications that worked? Noted that you said Cortana and 3rd party were not so wanted to confirm. Thanks for the post, this will probably influence my decision more though, as Fitbit has done a decent job trying to get their UWP working well.