The movie was plain average with only Music, Ranbir Kapoor's performance and few (extremely) scenes to cheer about. It is a total disappointment to see a talented film maker like Raj Kumar Santoshi making a waste out of best. I would thus agree with only half the title of the movie i.e. "Ajab Prem" (indeed Ranbir is fantastic). The other half "Ghazab Kahani" (story, comedy and rest of the cast) is totally misleading.
The comedy scenes do not appeal and look forced, the script is very weak and thin, there are no punches, the comic timing of actors (except Ranbir) is very pathetic.
We can skip over Katrina's mention who does not do anything more than looking good. This film provided her with equal opportunity to perform which she has royally missed.
Final Verdict: See it at your own peril