These cabins are terrible. If you book one of these cabins you'll have soot on your balcony, noise and a giant sea squid will climb up the side of the ship and eat you.
Seriously: These are great cabins and while you may experience a bit more vibration when the thrusters are engaged (going in and out of port) they are one of the best cabins on the ship. The balconies are usually larger. Many of them wraparound from aft to port or starboard and many of the cabins cabins are a bit larger.
As Trip let said, the secret is out and many more people are booking them and most of the cruise lines have recategorized and raised the prices on them to a higher level than the standard balcony cabins.
It's hard not to book one if they are available. I had one for upcoming Epic cruise but upgraded because of the reports of small cabin size for the BA cabins. There will be three of us and I'll need as much room as possible.
Book one and you'll never want anything else.