The first half was great, engaged me well, was fast enough so as to not get bored, and was slow enough that it didn't move from event to event unneccesarily.
The first half of the 2nd half was ok, used some gimmicks like tracking this, and tracking that, sending this and that, but still was gripping enough...............
the last 30 mins though.......
one thing few movies do is to explain each and every bit of the mystery, so the viewer can understand how much work and thought the crew put into the plot, but they miss the point, mystery movies are suppose to engage the audience, not hold hands and walk through each and everybit of the plan, and many scenes just repeat themselves, once in main film(police imagining) and again explaining..... unneccessary drag.
And the last twist wasn't even a surprise.
Ppl can easily guess it in the last 30 mins
final verdict: yes, ok watch it, atleast you'll get 90 mins of a good film! Even that is v good in these days.