Sky deck is great for running back and forth to the pool, just 1 deck up. But the overhang blocks out the sun and obstructs the view. My first balcony cabin was on Millie on the Sky deck and I was dissapointed. No problem with noise, though, and everything else about the cabin was perfect.
For my next cruise (Summit, 8/23 Alaska), I'm in 6144, which is a category 1C but with a deck that is 3x larger and open to the sky. Live and learn!