It's nice, I suppose, but when I'm on a trip they're so full, I wouldn't have room for them. Typically, I do take the topbox in with me and I have luggage in one of the side cases so that everything comes out in one piece. The other side is just tools. I could see it coming in handy if I traveled at night, but I try to avoid that.
You know, in thinking about this further, I'm going with those below this post. I think it's a good idea. I just ordered two packs from Amazon. Only two packs left.