I really like this coat and wear it almost every day, but there are a few problems.
I am 5'6", 160 lbs, and bought a size Large, which fits well. There is just enough room to wear a sweater under it but it still looks cute with a thin shirt underneath. It fits in a very flattering way, where it gets tightened at the waist with the belt and flares out. I usually button two or three of the buttons and tie the belt at the waist. The belt is way too long to buckle. If you buckle it, the tail on the end will be really long. I tie it in a knot at the waist and it looks good.
 It is warm enough for about 50-degree weather, and so it's great in the spring and fall (maybe in the winter if you live in California).
My biggest problems with it are that the buttons are really loose, and it's not waterproof. The buttons are not sewn on well, so most of my buttons have come loose in the year that I've had it. I need to sew them back on before they fall off, and I've lost one so I need to email Tommy Hilfiger and ask for a replacement button.
I also hate that it isn't waterproof. I bought it specifically to wear in the rain, because it's the only trench coat I found with a hood. Since I searched Amazon for a raincoat, and this popped up, I expected it to be waterproof. It will withstand a light sprinkle for a few minutes, but the water soaks in and a few minutes in any sort of real rain and it will be soaked through.
Overall, it's a very stylish coat, but isn't waterproof and the buttons fall off.