We recently completed a 14 day cruise on MSC Opera from Venice to Istanbul, Channakale, Istanbul and back to Venice. The ship and cabins were ok, but the food was terrible. The restaurant was bland but the buffet was swill. While there was plenty of it there was no flavour and some was just inedible. The staff in the buffet were lazy and did not want to do anything.
Probably the worst feature of the ship was the wifi, if you could call it that. Horrendously expensive for a service that so slow you couldn't even receive emails let alone send them. The timer would zoom downwards while nothing happened.
My advice is that if you are considering a cruise with MSC then go and find someone else.
Cabin was tiny but liveable. Cabin staff were good. Shower was the worst feature, unreliable hot water and a shower so small that you could not drop the soap.