For the above bag I used both a fuseable interfacing and a fuseable fleece attached to the outer fabric, first fusing the interfacing then the fleece. It turned out quilt nicely especially for this type of bag without any folds or pleating in the exterior.
This one I made interfacing the lining, and doing nothing to the exterior. It only works because the bag is so simple, and isn't that large. I like the idea in principle because I thought the bag would wrinkle/crease less and be easier to wash.
This over sized (quite over sized) tote I made using only fuseable fleece, but inserted a piece of timtexesque material in the bottom to provide more structure and stability.
I figure its important to experiment with some of the different products out there to see what works for my various needs.