My regular 50d Enigma arrived this weekend and I decided to sleep in it Sunday night. Although I am 74" and technically "should have" gotten the long, I got the mild weather quilt, and vary rarely sleep on my back so I wasn't too concerned about it's length. When I got in the quilt and laid out on my back with my toes touching the bottom of the bag, it came just barely over the tops of my shoulder blades (EDIT: It might have been up to my chin. I need to check this again). When sleeping on my side, I could pull the top up over my ears (as I recall).
Given that it is for mild weather use, I very much was less concerned about it being a little short. If I were to have gotten a quilt for colder weather, I would have likely gotten a long. But I trust Tim, and if he says the Regular length comfortably fits up to 5'-11", than it will probably fit you perfectly.
Finally, I am simply blown away by how light it is. I think it's lighter than the storage sack of the next lightest sleeping bag I have.