The 400ex's are good bikes.
I have an 05. I know people always say they're slow, but ill tell you what. With just the exhaust and timing key, I swear to god it feels snappier/quicker than the piped predator I rode.
It's fun to tool around on, blast some trails with, and screw around. I use it in my local trails. But at the coalmines and such, nothing will replace the banshee.