I also did a solo trip for the first time last year. I had a fantastic time. It's a lot of fun being able to take your time and look around the park at your own pace. I'm one of those people who needs to see EVERYTHING so I can drive my friends/family a little nuts when we travel, haha.
For me, I never really felt lonely in the parks. Like everyone above has said, people are in such a good mood. Eating alone didn't really bother me, but I just did quick and easy self-serve food. I might have felt differently going to Blue Bayou alone or something.
The only time I felt a little silly, as a grown 36 year old man, was getting onto certain rides solo in Fantasy Land. I did forego a couple of the kiddie rides because I think I would have felt a little dumb riding alone (like the carousel, ha). But other than that I rode everything. Single Rider is awesome. And I noticed that there are a TON of people riding alone. They may be on a solo trip, or their family may be taking a break, etc., but I noticed lots of people riding alone so at no point did it feel like I was the odd person out.
For me the only lonely part was getting back to the hotel at the end of the night and being there solo. But I was so exhausted by that point I couldn't really dwell on it, haha. One evening I did cut out of DLR early and took a drive up to LA, which was fun.
I highly recommend a solo trip. You'll have a great time.