We had the "horizon balcony" on the Silver Origin, and really enjoyed it. It gave us a lot of interior room for the large majority of the cruise when we kept the window up.
We would put it down during the daytime for short amounts of time. It worked fine. We weren't bothered by having the outdoors into our cabin, or anything like that. Frankly, we weren't hanging out in our suite much during the daytime - the open decks above were just too lovely. But I do recall several occasions of just lowering the window to look out at the scenery, or the water, or whatever.
The part of the room where the balcony would be still had the teak wooden deck, so I remember putting water shoes and other stuff out there to dry, even when the windows were closed.
It's an interesting concept, and something you should consider. But to each their own.