I've heard of this. I always wanted to go, but my family doesn't have the cash. I would have liked to see the Great Ball Contraption. Was it made with Lego's RCX or NXT robotics systems? Or did they do it with just motors and battery packs?
Also, we seem to have quite a few people here who build things with Legos. Maybe we should open an HLP Lego Build-Off thread? We could have a division for FS models, non-FS models, and maybe a robotics division. We would just need to set basic rules and find some judges.
It happened to be very close to where I live, so I didn't need to pay for lodging and things like that. The GBC modules I remember seeing all used only motors and the speed regulator units, although there may have been a few running on RCXs. If I have time, I might make a GBC module for the next event.
I make mostly conventional Technic models and Space stuff based on the official themes in the early 90s. I'm currently working on some upgrades to that Annihilator model, mainly adding another motor to power the stabilizers on it.
You should have done what GalEmp did in Penn Station when he was trying to find Su-Tehp, Splinter, and myself - wander around the hallways with a placard that read "HLP" in his hand. I can't even begin to imagine how many people saw him holding that thing up and thought that he really did need "help" if that's how bad his spelling was.
That would have been funny to see.

I had sent Goober my cellphone number in a PM, but I did it way too late.

RAWR @ BF07.jpg................................
I wantz it........... 
The rotors on that thing were actually motorized. It was pretty cool to watch in action.