It was terrible, in every respect.
I have no issue with the motion+ whatsoever, except with the harp. I actually got worse at it as the game went on. While I had slight troubles every now and then with the swordplay, it was easy to just recalibrate. The harp was always bad. It might just be me and a few others, but I found it almost unusable - and I'm not the only one. I haven't finished SS 100% because of it, due to the heart pieces. Call me unco, but it's true.
The songs were also particularly boring. I honestly can't remember any of them, and paid little to no interest. There was a poor interactive experience for the songs. Even the Howling Stones gave us some kind of interactivity. Yet SS' songs are supposed to be a major plot element and I basically play them all in the same way.
I was also sad to find that the songs were nothing more than collectibles, things that acted as a trigger for the story to progress. In games like MM and WW, different songs could be played to give real effects such as altering the time and the direction of wind. SS gave us nothing of that.
Overall, to say that the harp felt out of place is an understatement. After 10 minutes of fascination, it just didn't feel like it belonged at all.