Hell of a twist! It definitely makes things more complex and intriguing altogether.
It sure sucks that your brother is Michael's vessel and your Lucifer's, poor Sammy. I love how the writers are developing Lucifer's character; more calm and peaceful than the angels themselves, I mean he doesn't even try to get Sam to let him in by force like angels did with Dean.
I can do nothing but wonder, will it all come down to the ultimate brother to brother fight?
Shouldn't Castiel do what he did to Dean so Lucifer can't find Sam? (maybe he will when he finds out)
BTW an angel in a brothel? I guess you do can make that stuff up. ;)