We went on our first earlier this year. Two weeks around the med, with p&o on their new arvia ship, convinced by my mum and husband who rave about them. (Both very young at heart and both under 60).
Me and my DH hated it !!
You are stuck to a itinerary, the days you get at a port are very restrictive, usually having to book a excursion to ensure you arrive back on time (or get left behind), most places we had at most 5 hours to explore, sometimes we were spending the same amount of time travelling to and from places of interest as we got there to explore.
Many ports were disappointing with not a lot to offer.
Entertainment was dismal.
Many evening entertainment shows you had to book onto in advance and were very often full.
Food sub par unless in paid for restaurants and even then it was just ok. (Bar one steakhouse which was incrediable, the highlight of the trip)
Staff seemed miserable.
Everything is an additional cost. Activities onboard, drinks (unless you pay for a drinks package), internet, shuttle buses, even bingo - we paid £30 for bingo!
You had to be up at the crack of dawn on sea days to get a sun lounger. Despite them saying you couldn't save beds, everyone did!
Pools are tiny and kids constantly in them; I got hit in the face twice by kids jumping into the pool.
For me, a two week all inclusive somewhere where you time is your own, you free to explore as your own will and or relax, your food and drink is included and you can book excursions if you choose usually as much better value; the ones we booked was literally for a coach journey there and back and we were paying minimum £70 each time.
Also, I got horrendous sea sickness the first 3 days, it was awful. The only way I didn't throw up was if I was lying flat on the bed, and didn't move. That was with taking sea sickness tablets before we even departed and everyday too. It did subside, but I spent the whole time at sea feeling queasy.
I couldn't wait off and vowed to never do another one again.
If you're tempted; I'd advised doing a smaller one first - maybe a long weekend or week at most..
In saying this, me and my partner love to go somewhere and explore, we spend very little time milling around the pool or beach, we get up usually around 8.30, out for breakfast at 10, and then spend the day just going with the flow and won't return until 8-9pm after having lunch and dinner. It just really wasn't our idea of a holiday.