I don't see Rudy being any different on the environment than McCain. Both favor a "comprehensive immigration" policy. I view Giuliani to the left of McCain on most social issues (gay rights, abortion - including the partial birth variety - etc.). One of the advantages Rudy has is what he lacks: a voting record.
GOP members like Rudy and McCain used to be referred to as "Rockafeller Republicans." Now they are simply called RINOs.
I would agree with you that Rudy seems to be the left of McCain on social issues, that is if I could trust McCain. I would also agree that those positions cast him in the mold of a so called Rockefeller Republican. I don't think that is true, from what I have read and heard from him so far, that he fits that mold when it comes to economic/social welfare policies.
Time will tell. And with that, I'm off for the night :)