I have their (JRB) Sierra Stealth quilt, a 45F rated sort of summer unit.

JRB makes good stuff, or at least based on my one example. The flexibility of use is what drew me: head hole with velcro-like closure to allow the quilt to be used as a sort of serape. Draw-string footbox closure so that you can open it up to make a retangular quilt when that better fits your needs.

As hikinggeek said, shock cord can help to pull things in underneath you; I use this with a micro caribeener to easily attach/detach, and a sort of drawstring-adjuster on the other end so that I can tighten it up or loosen it in the dark. I much prefer to use the quilt without the shock cord, and only add it when I'm sort of pushing the temperature envelope with it.

What I think is particularly nice is that --- with the shock cord properly deployed --- I can layer this over my 30F rated sleeping bag to allow me to use that in significantly lower temps.