It was pretty fun; the controller really was the kind of magic sauce for what we wanted to do. It's very difficult to make games attractive and accessible, and I'm sure that 90% of what draws people into Guitar Hero is that plastic guitar. They instantly say, "I get it! I pretend to be a guitarist!"
Obviously this is much like what Nintendo was getting at with the Wii, but it can be easy to forget that when non-gamers look at somebody playing a game, they don't see those virtual worlds we get lost in, or the infinite calculations passed back and forth between our brains and the system's. They see some guy holding a remote control and staring into space.