I generally don't watch Ben Stiller movies - I don't enjoy humiliation comedy at all - and so approached this movie a little doubtful of whether I'd enjoy it. And, indeed, if it had kept to the tone of the original story I don't think I would have enjoyed it particularly.
But Stiller's Mitty is not a cringeworthy comedic humiliation magnet, nor a Mr Bean-type oblivious disaster, but a more rounded and functional person in an invidious situation. He has been worn down into meekness by an imperative need for money - someone who gave up his real dreams at seventeen in order to deal with sudden debt - and so the movie is a journey to finding that person once again. And it's a very enjoyable journey, a little surreal in places even when not in Mitty's dream world, but definitely worth watching, and populated by people who (the three 'beards' aside) seem quite real and ordinary and relatable in a way that few movies actually succeed in doing.
It also has some of the best use of music I've ever seen in a movie. Watch it for Major Tom alone.