I tried the demo and it got some stuff but seemed to leave the things for a couple apps in Application Support…works as well as anything else I've tried but the others are free.

Would love to see this work really comprehensively, so that I would feel confident about paying for it.

I voted to recommend it below but it still needs a little work. Also I would prefer it if it worked transparently like AppTrap (you just throw stuff into the Trash and it comes up with a list of associated files. But again relatively minor stuff).