I'm so sorry to dredge up such a tired meme, but you know it has to be said here.
Imagine a Beowulf Cluster of these!
In all seriousness, though, I'm really enthusiastic about the philosophy that seems to be behind this project. I'm all about replaceable parts. This would be nothing special if it was another "all in one" SoC, but the fact that it is explicitly a swappable *component* really appeals to me.
I love the open architecture, and I love the open hardware. The PCMCIA form-factor, along with the choice of "lowest-common-denominator" interfaces, give me the warm-fuzzies inside; the last thing we need is another homebrew data bus. I can think of tons of things that cards like these would be good for.