Just got mine and found the same thing. Absolutely love the Flyweight material and construction, but although I normally wear an XL shirt, a Large would have fit me better.
If you look at the sizing chart on their website, all shirt sizes run very large compared to most retailers.
I plan to order 2 more shirts, one long sleeve and one short sleeve for my upcoming hunt, but this time I'll order one size smaller.
Tina is pleased as punch with her ladies shirt from Kevins, but she was smart enough to look at the sizing chart for women.