The U3 website is one of those hardware industry initiative sites so overdesigned and inscrutable that I can't tell if it's promoting the idea of running applications right off a USB flash drive because of the idea's increasing popularity, or despite the growing demand.
There's some great directories listing all the apps designed for, or optimized for, running on a thumb drive. Jeremy Wagstaff's list is a great place to start, and if you can stomach the overwhelming amount of ads, TechTastic.ca has a good list as well.
The contrast is striking. Even the ugly TechTastic site has actual links to apps you can download today, while the U3 site has a form that lets you "Keep up with the latest U3 smart drives and smart software with our free Get Smart e-mail update."
That's not to say that U3 won't grow to be a really useful spec that's widely adopted. It just means that they're blowing the chance to demonstrate the real utility of the technology they're advocating, even in its current rudimentary and immature state.
I vote "in spite of." They seem much more interested in pushing their specific technology than in the base idea of running software off a USB drive, which is hardly new. There's already loads of software that will happily run off a portable drive, which will continue to have absolutely no need U3 drives; they're just self-contained programs. What a concept.
Also note that there are a good number of applications in this mysteriously link-free list that are already available, and already do run off a regular thumb drive. The important thing here seems to be that of the ones I tracked down, only one is yet promoting the as-yet-unavailable U3 back. Mystery solved. Wouldn't want anybody figuring out that the future is now, huh? Also, they're hyping the support they've gotten from the Mozilla Foundation, and ignoring the existing—presumably non-U3—Portable Firefox and -Thunderbird by John Haller.
Overall, it feels a bit disingenous and revisionist.
The idea is cool I suppose, however the technology has indeed been around since the days of the ark. not only do you get a myriad of different software that runs off thumbdrives, you get whole operating systems too.
Regardless of why the U3 site exists, I think that any initiative to make software that works well with read-only media is nice. I really enjoyed the lists of existing packages. I know I will be checking several of those out soon.