Hi Donna,
I'll just chime in here at the end…
When I had my Arc AT, the straps were not completely detachable, but they did have a snap closure so you could leave them open during the night. Typically, I used to just undo them all the way but leave them snapped together. To me, the straps were a nuisance but I wasn't about to cut them off because I figured if I ever sold it (which I did) the next persom would want them.
On my next quilt (The one Tim made me) he actually put removable straps on it and I have since taken them off. I find it easier to move under the quilt this way. I guess it is personal preference.
With regards to the measurements. I think you are asking why the width of a quilt is smaller then the width of a sleeping bag? If so, this is because a quilt is designed to be left open against the ground as a compressed section of a sleeping bag would not be insulating anyway.
I don't want to be the guy who posts his own links all over BPL, but take a look at this video. (Moderator: if this is not within BPL policy, feel free to remove it)
http://www.youtube.com/watch?v=g46SUD27nf0
It isn't a Nunatak quilt and some of the video may not be interesting to you but it will give you a good idea of how a quilt fits around you and how to use it. Also, you can compare the size of me to the size of the quilt and the coverage it gives me. Hopefully this will help answer some questions.
Steve
p.s. Quilts are awesome!