In my opinion, more than a beautiful place it seems almost like a unexplored land for tourists... and that's just amazing. I went there to have a look at the very ends of August, when some people has returned to Milano but not enough to feel that vibrating energy so usual of it, so I had to run away.
I've got to say that just one day there is perfect to have a first look of that side in people from North Italy that usually you don't see on other very known lakes like Como, Maggiore or Garda.
My advice? Rent a bicycle (if you can't bring your own) and take the boat to the island in the center of the lake... you will never forget it. There's always something to see in this lake, like a extraordinary second hand design shop with some exotic kitsch nice things.