@Scrbblchick -- I've never heard of these! Didn't know anyone ever made them. They do sound like they would do a good job, but I can see the complications of the whole butane concept.
They sound like one of those things that's a great idea, but it's almost more money for the upkeep (cartridges) than it would be just to plug the iron in. I don't know that I'd want to travel with butane in my suitcase, even if it is in a little cartridge. I assume they were very well sealed and all, but I'd still be a little leery of them, I think.
It would be nice if some manufacturer could come up with a similar idea that uses a better portable power source.