We had the Key on our recent Serenade cruise. Got it for $14.00 pp. on a Black Friday sale. We thought we would try it since I use a cane among other reasons.
There was a section in the terminal for Key guests to wait after the Suite and Pinnacle guests. I don't think that saved us a lot of time getting on the ship since it was before 11:00 and not a lot of people were there before we boarded. We are Diamond so we wouldn't have boarded that much later.
As soon as we got on the ship they had a Key desk with our information and we dropped our bags off with them. That was nice.
The Chops lunch in the MDR was very good and very relaxed. Enjoyed that.
We never used the reserved balcony seating at the shows. We had seats on the main floor we always went to that we thought were better.
No tender ports. We only used the Key escort once at a port to get off. No time saved since they were already letting people off.
Breakfast in the MDR was at 6:30 on the last day. It was very good. They didn't start the Key escort off the ship until 8:00. Our luggage was in a separate location so easy to get to. I really don't think this saved us much time though.
Would we do the Key again. No. Like others have stated, the price is too high for what you get even on a sale. Just our opinion.