Responding specifically to the question of whether people actually "download and use apps"... while I love my apple watch series 1 and wear it every day, I pretty much never use 3rd party apps. To me the apple watch is all about getting notifications, checking important info at a glance (e.g. date and time or my next meeting), and activity tracking. I hate actually interacting with the thing for the most part, and find anything more complex than dismissing a notification to be cumbersome. And since the series 1 only works when tethered to my phone, it's usually easier to go pick up my phone (which isn't too far away) than to mess around with my watch.

I think that changes a bit with the series 3 and LTE support. I would be willing to deal with cumbersome interfaces more frequently if it meant I could leave my phone at home and still have access to essential functions (phone calls, text messages, etc). And I could see myself downloading a lot more 3rd party apps to have with me just in case (slack, 1password, authy, etc).

The only thing stopping me from getting the series 3 is the fact that I get cell service through a cheap MVNO that doesn't support the apple watch yet. Hopefully it's just a matter of time now before it is possible to use apple watch LTE service with MVNOs.