I decided to drink from the Kool-Aid and I ordered away for two. I expect to see them in six months or so. The demand has been so high that the makers have not been able to keep up at all.
I do have two projects in mind for them. One is a SID-based polysynth. I was going to do this with an FPGA before, but the R-Pi presents an opportunity to make it a cheaper, easier, and more capable. The networking alone is worth the $35, as that means I can make a programming interface for the synth ("programming" as in making synth patches in this context) that I can just ssh into.
The other... Well, I have this dream of making an FFT-based sampler, where all the sample data is converted to FFT data before loading it on the sampler, then using a DSP to process it as notes are played, and then run through iFFT before the D/A. Based on what I know about FFT, this should be possible. May be someone here will tell me otherwise.
Anyway, that's what I'm thinking. I take on way too many projects.