The pattern calls for a lot of interfacing, but I used hardly any. I followed the pattern directions to reinforce the bag bottom with Peltex. I also used fusible woven interfacing to make the handles using my own favorite method, but that's all the interfacing I used.
I made my bag panels using a quilt-as-you-go technique inspired by Suzuko Koseki's work.
Most quilt-as-you-go ends up being soft like a quilt, but I made mine super-sturdy with a layer of cotton duck. I used the pattern pieces to cut panels from cotton duck. Then, I cut low-loft cotton batting 1/2" smaller than the canvas panels. I put the batting on top of the duck, then I added scraps of fabric one by one, straight line quilting over each piece as it was added and extending the piecing out to the edges of the cotton duck.
The result is a really fun and sturdy patchwork Weekender that can stand on its own, even without all that interfacing.
Before I made this bag, I had heard a lot about how difficult it would be. I found the construction of the bag to be pretty straightforward, but it definitely required careful reading of the directions and some sloooow sewing when attaching the various parts of the bag together. (She mentions several times in the directions to sew slowly, which I think is excellent advice.)
I was able to use a friend's piping foot, which made the process of both making piping and sewing it down much, much quicker than it would have been otherwise. I followed another friend's suggestion to make the staps longer (mine are 9" longer) which is just right for fitting over my shoulder.
I also got a lot of use out of my Clover Wonder Clips which are great for holding together layers too thick for pins.