I think this has been mentioned in earlier posts here.
1) recipient_delimiter doesn't work with virtual domains in Postfix v1. We should be upgrading the mail machines to Postfix v2 within the next few months, and at that point, we're likely to set recipient_delimiter to something (probably "+"). I have tested it with Postfix v2, and it works fine.
It would work for firstname.lastname@example.org (if it were set, which I don't think it is currently), but we don't encourage people to send mail from "email@example.com", since individual machines may come and go.
2) I am pretty sure that some people have gotten TMDA to work entirely within procmail, so it's /possible/ to get TMDA working right now.