I have to agree with your friend regarding Irene's age. I think Rachel is a great actress but she is young with a tendence to look even younger at times (which didn't help). It was particularly distracting in the finale because she looked youngest when she was in that tweed suit. Though if Ritchie did have to hire a younger actress for the role, at least he picked one that could actually act very, very well.

For me, in the end, Sherlock Holmes is a story about a friendship and as long as I get that strong, enduring friendship vibe for Holmes and Watson, I am a happy viewer (mind you, if it's slashy, than all the better).