Just got back from from solo trip - and have eaten solo many times at WDW. I also travel on business enough and have actually gotten brave enough to dine out alone without bringing a book
Calif. Grill - ask for seat at counter in front of kitchen - the chefs come talk with you, it was great.
Hollywood Brown Derby - had a seat in a back corner, overlooking the "main floor" which was perfect for relaxing and people watching over dinner
I think the experience at Alfredo's depends very much on who is there and how busy they are. I ate there alone for an early lunch, and the wait staff made it a wonderful experience - kept dropping by to chat - it was very nice, didn't even realize I had eaten alone.
Concourse Steak House (in Contemporary next to Chef Mickey's) , Yacht Club Galley and Yachtsman Steak Houses were good food - although at both places the seating was in the corner. Of the three I think for the steak - Yachtsman was the best. For the total meal Concourse Steak House had better salad and veggies (was also a little cheaper)
Rose & Crown was the only place that I've been at recently where I felt that the table was not great - right in front of the door to restaurant and behind the pub.
Flying Fish - ate at the bar which was good (full menu available) - I think I had made priority seating ressie but that was where they put me.
Artist Point (Wilderness Lodge) - eaten here alone several times, each time, have been seated near windows with view of Bay Lake and never felt odd.
I picked all the places that my friends don't often go and had a blast. I do sometimes bring postcards to write during meal or play with the kids menu.