I went on a solo cruise back in 2007 and had a fixed seating (earlier seating instead of the second seating). This was on Royal Caribbean's "Majesty of the Sea." While I did sit at a table for either 6 or 8, there was only another father / son type couple, for lack of a better term, that I sat with for the entire duration of my cruise.
I'm going on another solo cruise in about 3 weeks, and again am taking the earlier fixed seating. I'll see what happens with this cruise, but I enjoyed the two people I sat with on my last cruise, and even ran into them that first full day on the cruise up on the pool deck.
Cruising solo was a great experience for me, and will probably continue to do so, since my family's schedule conflict so much it makes it difficult to take a family vacation.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)