We have 2 insulated backpacks. One is a Coleman, that is a single strap. We got this at the outlet(14), but it's also on the website last I looked. We used this the last time at Disney, and it's not bad. The single strap is short for my husband and I though, as both of us are large and tall.
The other backpack is from Eddie Bauer. We got this at the outlet(20), and its a square backpack with the regular straps. It does keep things cold well, but I haven't had a chance to test run it at Disney yet. So I can't give you and accurate opinion yet. My husband finds the straps short for him, but there okay for me.