This dress fit true to size for me. I'm 5'11", 185lbs and the large fit perfect! The length is great too, it hits just at the back of my knees and just about 3" above the knees in the front. I have long legs, 34" inseam, so I always worry where lengths on dresses are going to fall on me.
The material is super breathable, with stretch and yet quite durable- not super thin.