Mixed review.  They sent me the short sleeve version of this shirt instead of the actual product, but it fits ok.
I'll probably keep it for summer and order another one and hope they send the right item.
I'm 5'10" 143 lbs and normally wear a 4/6/Small depending on brand, but for Asian sizes, I made a wild guess, ordered an XXL(US8) in this shirt and it was actually the right one for me.  I'm tall, and am pleasantly surprised of how long it is. No wedgies for long torsos!
Since it's not really that stretchy, even if I was 6 inches shorter, I still don't think the US6 size would fit me. My recommendation would be to definitely order a size up. Maybe two sizes if you're taller than 5'8".