Sky Suites 6145 & 6146 DO NOT have double sliding glass doors to the balcony. They ONLY have the single swinging door, and it is NOT a full length glass door either - just the top half has a glass window.
Additionally, even though these two cabins (and their balconies) are LARGER than other Sky Suites, their balconies are totally exposed with NO overhang whatsoever. What you do have is 3 decks of towering white steel bulkhead walls leading to the outdoor eating area of the Ocean Grill up on the Resort Deck. From there (as well as from the clear round porthole-like viewing 'holes' in the floor of the adjacent Ocean Cafe) people have a clear view onto the balconies.
We were EXTREMELY disappointed in this aspect of the ship's design, in so far as some of the TOP cabin CATEGORIES are concerned.
But on the positive side, the balcony is very large and contains 2 lounge chairs, 2 side chairs, and a table.
I don't believe there's such a thing as the Perfect Cabin. There are always trade-offs in terms of size, layout, location, noise, vibration, balcony door type, etc.
Personally, I'd prefer a cabin with a larger balcony. I was in cabin 9067 on the Millie, and the balcony too private--small with a large overhang--and I found it a little claustrophobic. (But, I loved the fact that it was just a few quick steps to the pool deck.)
I'm in 6144 for an August cruise on the Summit, and I'm looking forward to being able to stretch out and take in all of the scenery from the large, open balcony. To each his own--to me it just means I won't be able to sunbath naked.
We were in 6145 on the Summit. It had a full length door that opened out, two lounge chairs and two side and table. The balcony was large. We felt we had privacy. No port holes in the floor above. White tarps but people had to look thru to see something. No proble. It was a Great room!!!!!!!!