Me, too. I have a new HTC One M8 with SD card and love it even more than the Original HTC One. However, I still cannot get MC to synch with it under Win 7. I've tried different drivers from the HTC official ones, but to no real avail.
What I am doing takes two steps, one of which I already have to do in order to synch MC music with my iPad.
1) MC & iTunes Synch tool synchs iTunes, which I need to do for iPad.
2) Doubletwist app for Android and PC synchs with my HTC One M8 over the air (WiFi) very well. I have also been successful with Doubletwist wired, but the WiFi capabiltiy works better and more reliably.
Yes, this is unbelieveable unwieldly, but it actually works. Yes, it sure would be nice to have these new MTP devices work well and uniformly with MC, but the HTC One seems to be an outlier.
Now you know.
Still looking for a better solution... anybody, anybody?