If you guessed "animated character pipeline," you're right! Just like with every other engine I've ever tried, except our work engine, I ended up running into bugs in Collada import, making an animation that is smooth in Max, have nasty kinks when imported to C4.
I'm starting to become a little more frustrated with this area than should be allowed. OgreMax is getting there for Ogre, and I'm sure Eric will fix the C4 problems (he always does -- major bonus for C4 owners), and the kW X-porter for X files makes it reasonable to do your own engine, should you need to. Torque, I don't go near anymore, as the support is non-existent, and you have to wait years for updated tools for new versions of Max, which then don't work. None of them is Actually There Yet. This includes spin-offs of the above, such as Multiverse, using Axiom, using Ogre.
Here's a tip to anyone who wants to take over the game engine world: Make a working character art pipeline. Everything else is simple by comparison.
I'm interested because it's something I'm getting close to in my 2D art and programming experiments, and I don't really have much experience with animation to know exactly how I'm going to solve this.