I found Ae Dil Hai Mushkil thoroughly disappointing. Nothing about this movie connected to me. In my opinion, Karan Johar's Kabhi Alvida Na Kehna was the worst. However, ADHM manages to top even that!
Ranbir Kapoor and Anushka Sharma spend the first half imitating characters from Johar's previous movies and movies from the 80s while the second half looks like a retelling of Ranbir's own Rockstar (what with Ranbir eventually becoming a singer and the terminal illness track of Anushka)! Just disappointing! I think anyone could have played the role of Aishwarya Rai-Bachchan's Saba. There was nothing spectacular about her performance. However, I think she lets her eyes do most of the talking which is why Johar picked her for the role. She has this incredible talent of emoting with her eyes without saying a word which most actresses of today fail to do. Even her shayaris had no depth whatsoever. Not to mention she struggles with the Urdu portions. I don't think her role was even necessary as she appears in a 15 minuteish role. Ditto for Fawad Khan whose presence in this movie created such a furor prior to its release! Fawad is wasted in a role with which he could have done wonders with. Fawad lets himself to be overshadowed by Ranbir in some of the scenes that they share.
Performance-wise, it's Ranbir and Anushka's film. They own every scene that they have. However, it's the script that lets them down that they find themselves imitating characters from various old Hindi films! It's Ranbir Kapoor who rises over an inane script, leaving his own stamp in each scene which could have fallen flat in a lesser actor's hands. But then he has experience from his own movie, Rockstar where he also played a similar role, playing a lovelorn boy to the hilt. Anushka Sharma is good but finds herself trapped in a role that was done-to-death before a billion times in Bollywood!
On a final note, ADHM is just a one-time watch for Karan Johar and Ranbir Kapoor's fans. I felt like Johar cheated us by creating suspense about the plot of the film before its release. There's nothing novel about the plot of ADHM!