While some have referred to the arms being long, it seems as if the jacket itself is sized incorrectly. I am a typical medium, tried their M, and thought 'arms too long, lemme try a small.' Tried a small, and not only do the arms fit better, so did the body of the jacket itself. So based on that, I would say definitely get a size smaller.
Its an entry level rain jacket, not as waterproof and breathable as something you would get for over $100, but at the same time I thought it was more comfortable to wear with a t-shirt than those higher end jackets.