Has anyone ever tackled trying to do this?
Creating a relationship from Lead to Person Account (or even Contact) so that you could (especially with the Joined Report option now available) access data from Lead to PersonAccount to Opportunity (or Case)
Even if it's a plugin from App Exchange, I'd be willing to try it. I've looked at this randomly a few times in the past year, and it's frustrating that you've got the Converted ID reference sitting there, but not able to use it (nevermind the complexity of merged Accounts where only one reference to Lead could exist after the fact, among other things).
If anyone has any insight on magic they've done along these lines, I'd love to hear it. We're trying to avoid having to pay a ton of money for items such as GoodData which could do "some forms" of linkage between Lead and PersonAccount / Contact.