I love my brain bag/brain cell/freudian slip. It's a very good replacement and upgrade to my previous bag provided by my previous employer (a brenthaven).
Since you're always looking for ways to improve your products, I thought I'd comment on the waist strap: most of the time, I do not need it. I'm sure many other users are the same way. For example, a friend who has owned his Brain Bag for numerous years, whom finally convinced me that it was the way to go for my needs, ties his straps up neatly with an elastic. I copied him.
What I'd love to see added to the product is a place to stash the waist strap when not in use. One thought is a long narrow pouch behind the padding into which you can stuff the two strap ends. Another thought is just simply a built-in means to tie them up -- perhaps velcro or snaps.
Here's a picture of how I've got my ends tied up to keep them from dangling and getting dirty.