Digging up this thread because right around the time it was still active (4/2) is when I lost my original Note Pro. I had wanted to respond with test numbers but I couldn't without a unit in hand.
I've got my new Note Pro now and a couple of microSD cards to test and have concluded as I had described earlier in post #6 that the speed of the microSD card does make a difference when one moves up to the higher end cards.
In comparing a Sandisk Extreme Plus microSD to a Sandisk Ultra microSD I can confirm that the transfer speed to the Ultra is limited by the speed of the card. USB 3.0 vs 2.0 cable use makes no difference. However, with the Extreme Plus microSD card not only is transfer speed to the card faster than the Ultra but there's a slight yet measurable difference between USB 3.0 and 2.0 transfer speed to the card as well.
Details here.
I make no claims to this being accurate testing, it is simply myself testing file transfer times using a stop watch.