We went by (slow) ferry from Denia to Mallorca earlier this year, as part of a package as we live on mainland Spain. We had lovely comfortable, reclining seats in a lounge but probably because it was early in the season (mid May) most things were closed, including the main restaurant, which was a disappointment as there was only a self-serve very basic refectory-type cafe and one bar open, the latter being very crowded. The 'pool' bar was open as well, and we did find this very pleasant for the first hour of our trip, until the sun went down, as it was good to be able to watch the receding coastline that we were leaving behind.
Personally we found the 7-hour journey too long and boring, but with more to do on the ferry it would have been more bearable. We wouldn't do it again as we'd rather fly but it was an experience!