We chose to go on the MSC Seaside after having been on the MSC Divina. The price was next level cheap, a family of four with a balcony for seven days for $2379 (booze and internet included). Really we were motivated to try a new ship at a very cheap price. The reviews online were dreadful as I guess people only tend to review things when they are upset. We had a great time, we found everything clean, the entertainment was great, the staff was good, in general it was a pretty great experience.
I come from a cruising family, I've been on every major line, and average a few cruises a year. We've now travelled with MSC twice and I prefer them to NCL and also to Holland America.
I will say that MSC had the best kids program that I've seen so far. I haven't yet travelled with Disney but for the price, I really can't see how this company can be beat.
Clean and decently sized. The geometry of the bathroom was a little strange as toilet sitting may require one to twist slightly. The decor is sea themed with bright vibrant colours which may be distracting for some people. Some minor issues with the sliding door, but in general it was clean and new.