I’ve got one. My experience is closer to MTBrob’s than Ewan’s. It has got much better in the year I’ve had it because they keep updating the firmware.
Takes quite a while to find GPS on startup. Plays well with Strava, Bluetooth link to phone is much better in the last firmware. Screen is small so if you wanted to use it on your handlebars with the strap adapter would be hard, but fine as a watch. All day battery. The vibrate feedback for pause, start etc. Isn’t strong enough. Basic smartphone functions are useful so you don’t have to stop and root your phone out of your bag to read a text or see who is calling.
That’s all the pro’s and con’s I can think of.