More than once, I have used the USB creator, created from a downloaded ISO, and
got a nice USB stick which booted and was persistent. (In other words, when I
changed settings, they were still changed the next time I booted from the USB
stick.)

One of those times, the stick was brand new, and I had never done anything to it
to make it bootable.

I am running Mint 9.04. I think the USB creator is the one from Ubuntu, so the
fact I'm running Mint is irrelevant.

I have used unetbootin in the past, but the stick was not persistent.