As always I may be wrong (unlikely, but possible ), but as I see it the advantage of the Isostick (or of the Zalman, for that matters) is only for the easiness of the concept and easiness of use/preparation.
For single USB booting (say to install/deploy a single OS) a "plain stick" is "just as good", if not "much better".
For multiple USB booting we have by now software solutions (grub4dos or other bootmanager based) that cover if not actually 100% of needs, 98.37% of them (I like exact numbers, and I fake them in an accurate manner ).
What really takes me "off balance" is that, in my perverted mind, a "pro" (i.e. one that actually *needs* a multiboot thingy ) should have the technical knowledge to use the "normal" means (and thus need not an Isostick) whilst a non-technical-savvy user would find it a killer device and would *need* it even if he/she doesn't actually *need* it really.
I mean, it seems to me a lot like (most of) the historical nonsense of "unattended installs" and "Linux collectors".
Someone who is actually deploying tens of PC's a month may find more than justified the (non-trifling) time spent to put together a "perfect unattended" setup.
Any non-pro that may at the very most install one or two PC's a month can do a normal install (and have a coffee or take a walk and come back to the PC) alright.
Yet the number of non-pro's that go through the long and troublesome "unattended" install creation path is extraordinary high.
Someone who is actually (or wants to become) a Linux expert would logically (after having tested a few distro's) find a suitable "base" one and then learn to use it fully and to customize it along his/her own needs/likings.
Yet, if you look around, it is full of people with sticks with tens of distro's (that have exactly the same programs/tools inside) that the user has not the faintest idea how to use (and coming here asking help to senselessly add yet another distro - same as the many others already on the stick - for no apparent reason).
The only kind of person which may require multiple Linux Distro's on a stick beyond two or at the most three of them (a very basic one say DSL for low power machines, a "disk recovery" oriented one, say Parted Magic, and a "full" distro, say one of the tens of *buntu family or a Slackware) could be a technical journalist going to write a comparison article on the various distro's.
So, back to topic, besides the issue(s) that generated this thread (which I am sure will be soon solved ), I see the speed (or lack thereof) of the Isostick as a showstopper for the "pro's" to whom shaving off a handful of minutes from an install may make a difference.
If I may provide a generic suggestion to ElegantInvention, there is now (IMHO) a *need* for a "Isostick Mark II", with a faster data transfer (USB3?).