My trips have been part with people and part alone. There are plusses and minuses to travelling alone. The advantage is that you get to be totally on your own timetable which makes it more relaxing. If you're not a doormat, you'll meet new people and socialize.
The downside is that when something special or hysterical happens, you don't have someone to share it with. For example, I was waiting for a monorail and saw this girl who had done the "sunless" tanning thing. Well, she didn't do a very good job because the back of her hands were orange and the underside were white, white, white... and there was a very distinct line between the two sides. I had a couple of friends that would've been LTAO with me had they been there.
My last trip, I was very nervous about travelling alone (for the most part). This was the last week of February and I had been dumped on the Tuesday before Valentine's day. It was not a good break up at all. (Lesson learned: Don't date boys that are of a religion that's one step above a cult) Once there, I decided I was going to be completely outgoing, social, and was going to have fun. Afterall, I deserved it. And you know what? It turned out to be an awesome, and very fun adventure for me. I had an absolute blast and I'm not sure if I would have had as much fun if I had brought along a friend as a crutch. Side note: I'm not allowed to be dating with 2 months of going to WDW anymore. I've had two ugly messes right before trips. Bottom line, it's my trip and I deserve a vacaton and deserve to have fun. Doesn't matter who's there.