I once went alone to Magic Kingdom when I was body able; it was nice to do anything I wanted to do without asking someone else for their blessing, but it's no fun when you are the only one who is alone. Everyone else is talking to each other about how cool the ride was, and one has no one to talk with; not fun. Interesting experience to do it once. Only once.
Love, love, love the comments about extended family! The worst DL vacation we ever had was when my son was still in his teens, young enough to enjoy the park. I made the colossal mistake of inviting my sister to go with us on a trip. 3 days of hell. All she did was complain; her favorite ride was down for refurb, it was too busy, the fast pass was stupid.... Blah, blah,blah. We went on Splash Mountain, so we got to listen to whining about "chafing." Add in the after-park demands to find a liquor store, since she couldn't get a drink in the park. The day she left, we went to the park and didn't leave town until almost 5 pm, for a 6 hour drive home. Never again. Now it's alone (tons of fun), or with my daughter. This December, we're going with her boyfriend and his 9-year-old daughter, who has never been. I anticipate fun. Lots of fun.
Unfortunately, I have not come across many single rider lines so being by myself is not necessarily an advantage from that point of view. The last time I derived any benefit from being a single rider was the 4th of July, 2013 weekend when a ride op on I-305 called out "Single rider front row!" OK, here I come! I made my way to the head of the queue and people actually applauded! As to eating alone, that's not a problem - and as a vegetarian, I might have a problem agreeing on where to eat were I with someone. Finally, as to having my photograph taken to show that I was there, I have no hesitation whatsoever in approaching a total stranger and asking him or her to take a picture. Most are happy to oblige. I correspond by email with a coaster enthusiast from Canada who would not dream of asking a stranger to take his picture. Why on earth not? The worst they can do is say no. The only thing I regret is not being able to get a good photo of myself on a coaster (as opposed to one of those hokey park photos)because the ride ops are too busy to oblige and I wouldn't dare entrust my camera to a stranger who happened to be waiting in line and might or might not be there when I got off the train and tried to reclaim my property. And yes, I've gotten into some interesting dialogues with people waiting to get on rides.