I also have the same backpack (strange, same gear as F&F!). I have never used either the pack frame or the bag that comes with it. You are right, it is not expensive. If you are looking to save some coin, this is not a bad option.
I had a bad experience buying my first one from Alps Outdoorz. The frame was defective. They replaced it, and all is well with the world. It looks solid, and I carry it in my rig, just have not had a chance to use it yet.