I have a BLS bag, and it works fine. It's not perfect, but it's fine.
I also saw BLS made a duffel bag with it's track bag built in to one side. That seems neat, but I think I'd prefer it more if it were a backpack. I've been looking at triathlon transition bags and thinking they would be perfect for the track. I could fit all my stuff in the backback and easily haul it with me and still have two hands free.
I've been using a basic duffel and on big days, a folding cart to be able to haul my gear, track sack, cooler, chair, extra wheels...