I've only been to WDW three times, (see signature,) trip #1 was with my immediate family, trip #2 was with my whole family (including grandparents, aunts, uncles, and cousins,) and trip #3 was solo.
My favorite trip was my solo trip. My first trip, we only ate at one TS, Sci-Fi, my second trip we ate at CRT and Hoop Dee Doo all together, and then some of us ate at San Angel Inn and 50's Prime Time. I knew I wanted to try a whole bunch of other restaurants at the parks then and there, but I would never have been able to do that with other people. So when I go solo, I make at least two ADR's a day, and get to try all the places I want to, not caring about anyone elses likes, or dislikes. (My family would never go to Boma, and that's one of my favorites.)
Another thing is the rides, I get to ride what I want, when I want. For me, this meant numerous rides of Soarin, ToT, and Winnie the Pooh. Also, it was easier to decide when to get FP, and I could use the singles line, enabling me to use all of my FP in Epcot for Soarin, and not worrying about a long wait for Test Track, since the singles line never went above a five minute wait.
Also, I'm the only one in my family who cares about the characters, so I was able to get many more pictures and autographs then I ever had.
Another tip I could give you, is to make sure you have a park hopper pass, (unless you have an AP,) so you can go to park from park. Every day, except for two days, I park hopped, so it was well worth the extra $30 or whatever it was.
I could also leave or go back to ASMU whenever I wanted to, sleep when I wanted, I never had to wait for a bus, or worry about getting seperated from my group after Wishes/Illuminations/Fantasmic, when there's a whole mob of people, I could just move semi-quickly, and always got on the first bus.
Hope this helps.