Went on Discovery 2 last year - Eastern Med and loved it so tried Western Med this year. No complaints. Food excellent, staff superb. Relaxed cruise and would recommend. Entertainment hit and miss. Loved the comedian but didn't like the crew's musical. Squid and Anchor pub was a popular venue, got quite busy. Personally would only cruise for a week. We did cruise and stay and stayed in Sorrento after the cruise which was fab. Had an outside cabin with a window and it was more than adequate, not luxurious but you don't spend much time in your cabin.
Discovery and Explorer quite similar. More restaurants on Explorer but missing the lovely Atrium on the Discovery. Swings and roundabouts really. If I had to pick a negative it would only be in relation to the ports on this cruise. They were all commercial ports and if you didn't choose to do the excursions on offer which were quite expensive you had to get a bus or taxi to get off the port. The ports of call we visited in the eastern med, we could just walk off the ship into town.
Everyone - guests and crew were so friendly and if you had a problem they would sort it out for you.
No frills but adequate, clean and very comfy bed. Towels and bedding changed regularly.