I just wanted to let you know that I used the quilt and it worked very well down to 34*F. Although there was the occasional draft around the shoulders I did not get cold, mainly because of the layers in which I sleep and the fact that I am accustomed to sleeping in much colder temperatures.
I can imagine that for somebody taller (I am 5'9") I can see how it might be considered too short (altho plenty long for me), but I am keeping in mind that using a quilt is a lot different from using a sleeping bag. For this first foray into quiltdom I followed the mfgr guide and inserted the NeoAir xlite (regular 72" length) into the quilt with the cross-crossing cord cinched up only enough to keep the edges of the quilt under the sleep pad. Somehow, some way, the cord lock on mine was broken, but it was easy enough to tie a simple overhand knot to achieve the same thing. I did not use the snaps to snug up the top part of the quilt because I tried it temporarily and it was too restrictive for my tastes. As it turned out, however, the bag is so supple that when I turned on my side (I toss and turn a lot when I sleep) the bag just draped around my shoulders and kept drafts to a minimum.
What I did find rather cumbersome was getting into the quilt, which - with the criss-crossing cord cinched properly for the sleeping pad - required me to sit at the head of the pad, insert legs into the top of the quilt/pad combo, then worm and wiggle my way down into the sleep system. Not a huge deal, but a new experience.
A couple of things I am thinking of trying later: 1) do like Ray and remove the cords altogether 2) use some light shock cords crossing straight across the quilt to the corresponding eyelets, tensioned only enough to keep the quilt edges in line with the pad.
Overall, I am very happy with my first experience using a quilt. I feel that the 30*F temperature rating is accurate, and am sure that I could have slept with one or two fewer layers (I use very light layers) and remained very comfortable. The Siren compresses down to a very small in the bottom of the pack with simply the weight of items on top of it. I used the stock stuff sack, which is very light except for the stiff nylon strap and buckles used for closure, and will try it with a Zpacks Cuben dry bag. But it might be a few months before I use it again in the field because the weather has warmed up considerably of late, hopefully remaining so for several months to come. For the warmer conditions, I have the MH Phantom 45.