For those saying Monk acts like a cartoonish two year old- you are missing the point of the show. I am a therapist who also suffers from OCD so I have personal and professional knowledge in mental health diagnosis. Usually I hate portrayal of mental health diagnosis in television and movies because it's portrayed inaccurately and mostly does more harm than good in stigma. However, Monk is one of the only exceptions. Monk walks the line of making fun of a disease that takes the joy out of most things without mocking it. Besides some exaggerations (which is to be expected in a TV show); Monk is mostly accurate in its representation. OCD is multifaceted- there's 4 types that present differently for each person (Monk displays all 4 types). I couldn't be more different than Monk yet somehow, felt understood. It made conversations about OCD easier to have with my family and friends. I was able to show them things I felt that I found hard to explain myself. Sometimes the intrusive and repetitive thoughts can be so loud it is hard to concentrate on anything else. This explains why Monk displays erratic, selfish and sometimes, annoying behavior (much like a 2 year old).
If you understand this show, if you love, miss and wish it was on for more seasons- this movie is for you. If not, skip it.
P. S- while Psych and Monk have some overlapping features, they are different shows and should be treated as such. If you like the Psych movies/ show that doesn't mean you'll like Monk and vice versa. To compare them is a disservice to both shows.