Bag or Backpack at Disney World?

[ZoZo]

I carry a small backpack, and am able to fit in everything I need (including a light sweater).

You can bring it with you on rides; for those rides that don't have a storage area at your seat (like Soarin', which has storage underneath each seat) , just set it on the floor of the ride and loop the handle through your leg. I've even done that on RnR (which goes upside down!) and have not had a problem at all. Just make sure all compartments are completely zipped up.