I am 26 and love going to WDW solo. Sometimes my friends make comments that suggest that they think it is a little sad, but I take a breath and explain that I need "me time." I should note that the people who make the solo = sad comments usually want to invite themselves onto my trips and have me plan the trips for them. What I really want to tell them is "I prefer going by myself, because when I take you I become designated tour guide and then I don't have as much fun." I don't always go by myself. I like going with my parents and one friend of mine, since we seem to have the same Disney schedule, if you know what I mean.
Mini Rant: So I have taken a few people to WDW for their "first time" usually when we come back they tell me that they loved it. A few months later they tell me that they loved the trip and they want to do it again and bring some of their friends and let me be tour guide again, because I did such a great job. I know this is supposed to be a compliment, but honestly, I hate being tour guide. I hate the assumption that I enjoy planning a trip for several people who don't have the scheduling preferences that I do but still expect me to hold their hands the entire trip. On my last trip, I felt like I was going with a 2-year old. My friend couldn't go back to the room by herself, so when she got tired at 10PM, back to the room we went.
I need to find more commando people with which to travel.