DH and I went on the Thomson Red Sea Magic cruise last year.
The ships are well cleaned and comfortable. Food is varied and plentiful, and you can do self service or more posh dining. They operate a cashless system, so you put all your bar drinks etc on a tab, which you pay off by credit card at the end of your trip. There are several bars, a disco, and a show lounge where they do the cabaret.
I particularly liked the talks we had on board about the excursions we could go on, by a university lecturer in ancient history, giving us background of the civilizations, and also how to get the best from the experience, ie agree a price in advance before you get on a camel! You are expected to pay for the privilege of photographing said camel and so on. (This was in Petra, Jordan) The excursions are pricey, but well organised, and the local guides they employ are very good (we have found this on most Thomson holidays)
You have the freedom to do what you wish on board, you don't have to do activities if you don't want. Depending on where your cruise stops, if you're in a city port you can disembark and go shopping or to a beach, but sometimes on some cruises you are docked in an industrial port and therefore not close to towns/cities, and the trip coaches pick you up to whisk you away if you're going on the excursion. On the plus side, ship can be very peaceful when they have gone, more sunbeds available!
There are shops on board but they only open at certain times of the day and carry limited stock and range of things. One tip I found on a cruise website was to take things like san pro with you, in case you are caught out, at sea, and the shop is shut! Also enough prescription meds.
I think the only annoying thing I can think of is being constantly photographed, and the results being displayed in a gallery, waiting for you to by them as souvenirs.