Mousefest is really fun, but because of that it has also gotten really big. To me it was more fun when it was smaller, but that's just the way most group things go. It is still very much worth going to, though. And if you weren't there when it was small, you won't know any difference.
If you can, register for Mousefest and try to go to some of the smaller meets. If you are into hidden Mickeys, go to some of those meets/searches. Steven Barrett is an absolute sweetheart, and so is his wife Vickie. You couldn't meet nicer people. We have become friends over the years and have met up at other times of the year for meals, etc. I always look forward to seeing them every December.
Deb Wills is also wonderful, but obviously very well-known, popular, and also busy since she is one of the main coordinators. But definitely plan to meet her at some point - at a "smaller" meet if possible. She is so very kind and generous.
If you are into trivia, go to some of Lou Mongello's meets. He and his wife are also so very kind and genuine. But there are some serious trivia buffs out there, so don't plan on winning any prizes unless you are a dead serious trivia addict

. But definitely plan to meet him.
Another great guy is Len Testa from the Unofficial Guide and other places/podcasts. He's great fun, and after all these Decembers of seeing each other he even spotted me out of the blue at Epcot on a non-December trip. That was a thrill for me - to turn around and see that it was an Unofficial Guide author hollaring out my name unexpectedly outside the Mexico pavilion. We didn't even know that each other was at WDW.
There are others, but of the participating authors/webmasters, those are the ones who I make a point of seeing each year. The Passporter people are also really nice, and while we recognize and greet each other every year (and usually keep running into each other), I haven't gotten to hang out with them as much over the years.
Also, I don't know if anything is going to happen because it still sounds up in the air, but there's a thread here on the DIS podcast forum about a potential DIS meet, which may or many not officially be part of Mousefest. Here's that thread
http://www.disboards.com/showthread.php?t=1954182.