I really like how you left Windows Phone out of the mix there. As someone who currently has a Windows 10 phone and a tablet that runs Windows 10 I think you are being over optimistic. I remember one of the big selling points with Windows 8.x on tablets was the ability to have the desktop on your tablet. When my tablet was running Windows 8.x and it would switch over to the desktop, it would absolutely infuriate me. I wanted the metro interface on my tablet and my desktop on my desktop computer and laptop. And when I did try to force myself to accept and like a desktop on a tablet it just angered me even more because of how bad it functioned.
When the update for my tablet hit I updated it to Windows 10 and they finally had it where you could put it in a tablet mode, but the damage was done to me by then. I had picked up a Chromebook and fell in love with that it. I haven't touched that tablet in months, I have zero interest for windows on a tablet now, and I don't see any compelling reason to turn the tablet on and use it anymore. Seriously, I updated the tablet to Windows 10 and then used it for about 10 minutes, kind of shrugged my shoulders and went, "Meh," powered it off, put it up and haven't thought about it until today. What is so special about windows on a tablet? As I sit here and think about it I cannot think of anything which would make me want to stop using my Chromebook or abandon my Linux desktop to spend time on that tablet.
Then there is my Windows Phone, or Windows Mobile, or whatever MS is calling it these days. I started on WP7 and it was cool because there was a decent modding community and you could put custom roms on your device. Sure, it didn't have some of the features that iOS or Android had, and it was lacking 3rd party apps, but it at least had a cool modding community. Then came WP8 and MS shat on the modding community with their secure boot BS. Out went the custom roms, cool stuff, and the community. Still WP8.x lacked some of the features that iOS and Android had and still lacked good 3rd party apps. Don't misunderstand me here, there are 3rd party apps in the windows store but most are total crap that is either spam of some sorts or is now abandon ware. I will say I liked WP8.1, I found that alright just needed to 3rd party apps. Then they dropped WP10 and the update hit my phone so I eagerly updated. I LOST functionality on my MS Band.My MS Band works better with Android now then it does with my Windows Phone. I hate the layout of Outlook in WP10, I hate the layout of the messaging app in WP10. I also hate the layout of the dialer. In fact, I hate the layout of just about everything in WP10, it's so backwards and unintuitive. Now I have to clear notifications one at a time instead of clearing them all at once. Still shit apps in the apps store. What the heck is up with the one handed mode? It's more annoying than helpful. Cortana and dictation no longer work. Still no modding community. I pick up someones iPhone and I say this phrase about ten times, "Wow, I wish my phone did that." I pick up someones Android and say the same thing. But, at least my WP has a decent battery life, I am going to attribute that to no apps worth running to drain your battery.
Window Phone 10 is just as unimpressive as Windows on tablets it.