I was looking for a lightweight warm sleeping bag for backpacking and backcountry hunts. The Nemo Tango was the perfect choice.
The Tango packs up smaller than 14x7, weighs 1lb 12oz, and is super comfy. I have used it in temperatures down to 30 degrees and have stayed "comfortably" warm. It has a removable hood that is a great way to shed weight when temperatures stay above 40-45.
I haven't used it on a summer trip yet. I imagine it would perform fine though. I can regulate my body temperature easily in it by stick a leg out, taking the hood off, pulling the quilt down, etc...
All in all, I think the Tango is a very versatile 3 season quilt.