Admit to being a bit apprehensive when reading some of the negative reviews but were pleasantly surprised with our first sailing on M-Class.
We especially loved our Concierge Cabin on 8th deck -- Had never tried Concierge before (although we have tried Balconies) on Solstice and Eclipse -- but the price dropped after final payment and we grabbed the upgrade. Would do CC only if the difference in price was very small since the other amenities don't mean alot. On S-class Concierge doesn't add any square footage. We travelled with our grown son who was on another deck in a 3rd floor Oceanview -- he liked the cabin but said it was a bit noisy with vibrations. We had a nice steward who did a fine job.
There is nothing like sitting on the balcony -- especially with the enhanced Concierge Room Service menu (and it is terrific with smoothies and fresh french toast & baked bananas, etc.) -- we had a slipup and didn't get delivery and had to really scramble to find food in the buffet before an early excursion. I'm joking, it is easy to find food any time on the ship but we were running low on time. And we got one of the only surly people I met on the ship behind one of the waffle irons who didn't want to make me a fresh one when I could have one of the undercooked cold ones sitting in the tray. When we followed it up after the excursion found our order was sitting in someone else's cabin by mistake. The problem I had was that room service said that they never received the order -- Guest Services apologized and made it up to us. Our son said he liked the breakfast buffet very much.
Cabin 8084 - Closet ok, Bathroom ok - shower curtain instead of glass door. Small balcony but Wonderfully quiet room on quiet floor midship - Larger Concierge balcony cabin