Just got back from my first trip with my new Side Effect. During this trip I determined that 1 Side Effect + 2 S-Biners == great way to keep little fiddly things (earbuds, iPod, gum, pens, notebook, tissues, snacks, makeup bag, etc.) handy during a flight. One side of each S-Biner clips into one of the webbing loops where the SE's waist strap is supposed to go, and the other side hooks over the edge of the seat pocket:
My hand sanitizer is clipped to the S-Biner on the left, because I always assume that the tray tables and armrests on planes are filthy. That thing to the right of the SE is my water bottle, which holds 1L, rolls up flat, and has an attached clip. This setup worked out well for me -- I never had to pull out my purse during the flights, nor did I have to spend any time fishing around in the seat pocket for stuff (ew).
Unfortunately this only works if you already have adequate leg room (yes, I was sitting in my seat when this photo was taken, and yes, I am short).