I have to say that I'm a huge fan of the, "Well, done that whole evil thing... time for something else now!" 'redeemed' villain. Mostly because -- like you -- I've never really bought into the morality of suffering. I think it's used inelegantly as a kind of 'moral equaliser' by attempting to teach the villain empathy by force, with the assumption being once s/he internalises suffering s/he will be less likely to inflict it on others. Or something. And it just doesn't work for me.

Pain doesn't equal redemption, but someone using their own free will to look back intellectually over their lives and think some variant on, "Well, that's not working, now is it?" as the catalyst for some great behavioural change? That's cool.

Plus, yanno, it really confuses heroes, and that's always fun for a story. ;)