I did the June 27 - July 9 Grand Mediterranean Cruise from Venice to Barcelona as a solo traveler. This was my first cruise but I have been to Europe many times before. I had a marvelous time. I met lots of people (which I don't when I travel solo on land), got to keep up with my workouts, had a spacious room all to myself,and went on two of the ship's excursions.
The main restaurants were hit or miss - steaks were great, as was the chocolate raspberry truffle cake. Other meals I had there were average. Service was often slow. I truly enjoyed the buffet was Raffles Cafe - good variety of Italian, Chinese, Indian, and American food. Desserts were missable. Breakfast was always excellent.
Spirit is not a huge cruise ship, so I saw many familiar faces. You have to grab a pool-side lounge chair by 8:00 AM, especially if you want to be in the shade. People did put a towel on chair then leave for two hours, but I can't realistically see how the ship's personnel can prevent that from happening.
I only went to three of the evening shows; most of the others were musical performances and I skipped them. I saw a wonderful (albeit too short) magic show and a Flamenco performance (not enough stomping).
The two excursions (Istanbul and Barcelona City Tour with hotel transfer) were worth the price for their convenience - I discovered that visiting an unfamiliar port in one day by myself could be really frustrating.
The ship docked, cleared customs, etc,and let those not on ship's excursions disembark at each port in about 30 minutes. The only snafu occurred at Mykonos, when only two tenders were operating and it took two hours before my tender, 14, got to the island. Since the ship did not even arrive at Mykonos until 2 PM, no one got to stay on the island for very long. Several passengers missed the ship.