I have one we bought a few years ago with wide, padded straps. I think it is actually a hiking backpack, but I'm not certain. Anyway, I will probably continue to carry it while on vacation even when my little one is out of diapers.
I find that it is comfortable to carry, and I am able to carry all that we need. If I have a full pack of wipes, it feels heavy. My only other complaint is that it can be hot in the summer. Sometimes, dh will take over carrying it for awhile.
I can't see not having it anymore. I have to keep an inhaler handy, as well as headache and sinus medicine. When you include cash, credit card, license, and keys, it's more than most people can carry comfortably in their pockets. Since I have it, I also bring extra ponytail holders, chap stick, and (when at Disney) I carry ponchos and glow sticks, etc. since I can't really tell those kinds of things are there.