Is it though? I know a lot of pundits like to use the phrase "Post-PC", but I think of it more like "Post-OS". I am in the exact same boat as you, except that I have a Nexus 7 in addition to my Surface Pro.
Contrast that to 2010, when iOS was much more compelling at the tablet and phone level. Android, Windows Phone and Windows have pretty much caught up, and I love how all this competition has created consumer choice. I can pick the device that best suits my use case for computing, tablet and phone.
In 2010, I was all-in on OSX, iPad and iPhone. Today, just like you, I'm using three OSes. Moving data between the devices is painless. In my mind, there's really no need to go all in with a single company's ecosystem any more.
You can get away with any hodgepodge mix these days if you want, but it's still more convenient to match.
I know a lot of Mac users who would beg to differ.
I use Dropbox, Google Drive and OneDrive across all my devices, and I don't have many complaints at all. YMMV, of course. My use case is probably much simpler than yours.
Also, of course iTunes isn't greased lightning & a buttered dream on OSX, it's just "less awful", or so I hear.
That said, one benefit to a mostly homogenous ecosystem around apple devices, at least for me, airplay and streaming media across devices with less work (I get lazy about home it issues)
So don:'t get me wrong, I kept the surface, but my dream tablet is 13-15" with a pen that runs OneNote on Mac ;-)
Oh and for Android dev, turn off Hyper-V and install Intel HAXM to speedily use Intel simulators. That said, for testing on device, it's really fast with Android, no signing issues as with iOS, though they're easily overcome too.
I would like a bigger tablet, but I run all my Retina Macs at max resolution so 1920x1080 at 10" isn't really a big deal for me, you know? The biggest complaint I have is the idiotic DPI controls on Windows. They're stupid, and Photoshop is extra-bad at them.
Also, oh my god is OneNote wonderful with that pen. It is so good.
Mac laptop, Windows tablet, Android phone. My digital ecosystem is confused.