FWIW, shortly after I enabled UWP MIDI, I experienced a BSOD (first I'd ever seen in Windows 10, so a novelty if nothing else). The cause was DPC_WATCHDOG_VIOLATION. I restarted the PC and it's been fine so far. I'll investigate further only if it happens again. At this point, I have no idea whether it was UWP MIDI related or not, of course.
 

I must use MME.  UWP will not recognize my Behringer X-Touch or Frontier Tranzport control surfaces. 
 
 

Enabling UWP disables my A-PRO ACT device
So back to MME for me
 

Midi UWP implementation in windows has a long way to go. It doesn't seem to work with many devices at all (it doesn't work with anything I use). I think it was a very wise decision by Cakewalk not to default to it. 

Seems to work fine for me.   I have a VS-100 and an iConnectMidi4 connected.
The management and port labeling for the iConnect is improved.

It didn't work for me and I have a Cakewalk UM-3G MIDI interface (and some USB MIDI devices also). So I had to go back to MME. If there are valuable features in UWP, then somehow the bakers need to figure how to make it compatible with MME or at least explain how we can get our projects working with UWP, if that's even possible. Let's hope they don't take away MME any time soon. This is probably just version 1 growing pains. 

mudgel
And we're a long way from Windows 10 being the default OS for Sonar users.

Just an FYI - check out the September 2016 eZine top 10 operating systems for SONAR users. An excerpt:
 
#1: Windows 10 – 64 Bit
 
With an almost 3:1 lead over second place, SONAR users are voting with their wallets and going for Windows 10. Although actually, it’s probably more accurate to say they’re not voting with their wallets because they likely installed Windows 10 when it was a free upgrade…but you get the point. In any event, this may also help explain the general consensus about SONAR performing very well—it seems SONAR and Windows 10 were made for each other.

And I always like to point out that Windows 10 is still free to those who use accessibility features like the Magnifier. 
 
I will also say that I use both W7 and W10 equally and I really don't notice any difference in how my software behaves at all. My 3 Desktops are all W10, my 2 Laptops are W7 and my little netbook is still XP. All perform smoothly and without issue day to day. Only W10 will cause me grief when it updates and re sets all my preferences :( 
At work we will be using W7 for at least another 5 years or more according to the IT dept.