Real-time audio input: good for you, that’s a nice starting point.
Why is your frame rate so poor, though?
See the related Dandelion project by the YOKE collective: http://www.youtube.com/watch?v=qnpgLwqfKMU, http://www.youtube.com/watch?v=Nza0vG5amro&feature=related
Consider removing the flocking “separation” force (is it really appropriate for this metaphor?), and consider adding a small amount of noise (or better, using the noisy variation in your audio signal) to keep things from clumping.

I like the bars in the background. I think it’s subtle enough to not be a big distraction.

If you used GLSL you could increase the number of particles dramatically. A reference for game developers: http://www.2ld.de/gdc2004/MegaParticlesSlides.pdf

I think this could be really beautiful if you applied a 3d transformation to it as the particles bounced. What if the seeds slowly moved away from the stem and the image of the stem got smaller and smaller?

i’m not sure what it would look like, but it might be worth seeing what the bars looked like smoothed and curvey

It’s hard for me to see how the sound relates to the dandelion pods

Have you thought of any other interaction instead of music and the dandelion?
Maybe wind from mini fan or mouth have better connection to it and make it more interesting.

It looks very calm and beautiful, although I wonder if that is appropriate for all sound environments. Maybe if there is a lot of sound (a cacophony) the background color changes to something less peaceful?

What decides the size of the seeds?

It might look nice if you made each seed look a little different

My favorite part is when the particles first come off the the stem, but this happens only once. maybe if it got absolutely quiet for a bit, the particles come back and land on the stem again.
Or another stems sprouts? Yeah!
-If you hit the spacebar, it resets. If it’s dead quiet for a while, it resets as well. 😉 – Amanda
That would be really nice.
I wonder how you could use the sound of the natural environment to create a virtual ecosystem of dandies.