It just depends on the type of person you are.
For me, it's heaven. Pure and wonderful. I love traveling to WDW with others for different reasons, but a solo trip is just insanely fun for me because I've got my childhood fantasy at my fingertips and whim.
Then again, if you are someone that can't even go to the movies alone, then you might not enjoy it. I've traveled for business and school alone so often that I literally don't even give a thought to walking into anywhere alone. If I want to be social, chances are I'll find someone to be so with, and if not...I have no problem sitting at a table eating a full-course meal with only my water glass as company, LOL.
What I like most about touring WDW alone is the selfish need to re-ride the same things over and over. Like, sitting on the TTA for 5 or 6 revolutions around the track if I feel like it. Or, deciding on a moments notice to catch transport to another park because I want a change of scenery.
Touring WDW with others certainly is it's own massive enjoyment, and touring solo isn't for everyone. For me, there is so much to see and do at WDW I'll enjoy it either way; each has it's own unique benefits.
AEfx