We did a 7 day Med cruise 2 years back and it was honestly one of the best holidays I've ever had.
It was with TUI on the newish Marella Voyager, and as someone who hates crowds and masses of people, I assumed I would hate it but it was just awesome. The ship never felt rammed, we queued for nothing and it was all very clean, well ran without issue. The only downside was feeling ashamed at how well you are treated by the lovely crew staff who seem to be worked to the bone. They could not do enough and it made me slightly uncomfortable at times.
We did go on adults only which probably helped with the stress levels, but I am chomping at the bit to go again and would love to go further afield.