Series Brilliant
How do you make a relatively light-hearted series about a private detective with OCD and a deceased wife who solves crimes without descending right into schmaltzville? You do it the way Monk does it. Sure, this premise would be incredibly easy to screw up. The main actor could come across as insincere, and the scripts could be filled with cheap moments of sentimentally that make every one in the audience want to wretch. But this doesn't happen here.
A lot of credit goes to the actors, who are all excellent, especially Tony Shalhoub who has the portrayal of his character down to a fine art. But the script writers deserve praise for not making Monk an "inspirational" character. He has unrelated personality flaws, and his problems aren't particularly dramatic. They're mundane and can be hard to sympathize with for those who don't walk in his shoes, which is shown in the series by the reactions of the people around him. The supporting cast treats Monk like how he probably would be treated in real life. Those who don't know him frequently have No Sympathy, as many can and do in real life. But most of the people that know him at least try to accommodate for him in a way that isn't patronizing, especially Captain Stottlemeyer, who consistently treats him like the fellow detective that he is.
Thus the strong characters make a compelling frame for the mysteries, which are engaging and well-told. The series usually showcases classic fair play whodunnits, with the clues and details able to be picked up by astute viewers along with Monk, which is quite against the trend of some crime dramas that play their cards close to their chest through exaggeratedly exact forensics or the like. This makes the resolutions of the episodes more satisfying, because there are little to no ass pulls. Another unique element was the greater overarching mystery of his wife's murder, which helped to give the series a center that a lot of other shows in this format lack or lacked at the time of its production.
Overall, Monk is a well-played drama filled with compelling mysteries and genuinely heart warming moments, all because it doesn't talk down to its audience.
Series Tasteless
Monk isn't just an incredibly inaccurate portrayal of OCD, it is an insult to those who truly suffer from this serious mental illness. The show completely ignores the obsession part of OCD, and Monk's compulsions consist of only the most stereotypical. The writers use Monk's compulsions as punchlines, and, as one poster on the OCD forums put it, the way Monk acts "just fuels the stigma about how all OCD sufferers are all eccentric, reclusive invalids." It trivializes the hell that those with OCD go through every single day.
No one would ever write a comedy show about someone with a physically crippling disease, because that would be insensitive and rude. But apparently, it's all right to write a comedy show about someone with a mentally crippling disease.
Watch something else.