I loved it! I thought it was one of the strongest episodes this season. I was thrilled Mary had a chance to explain herself - I'm back to enjoying her complexity. The boys were great and I'm loving the BMoL storyline.
I feel like there's so much to say I just don't know where to start. So I'll leave it for any discussion that might, or might not, happen. Ask me questions and I'll answer them! :)
The only thing I'll say is - it's worth noting that Sam and Dean don't know what we know about the BMoL. The only experience they've really had is rogue Toni *weeps*, other than that they know they have cool gadgets and they want to rid the world of monsters. And now Mary is on board. It made sense to me that Sam said "I'm in" at the end and I suspect Dean will get on board as well (they were hinting he would in that episode). It could be that Sam can see where he and Dean could help them, or that it's better to be on the inside of this outside force. Either way I'm excited to see where they go. It's got great potential (and why I wish Berens could just write all the eps so there's one vision/thread running through the show).