Just for my own edification, since you seem quite familiar with the subject: Is Obsidian* a big fat waste of time that'll never be as good as just compiling Haskell for a CPU like a normal person? 'cause I was considering investing some time in learning it, when I wouldn't have the free brain cycles for CUDA.
I didn't know about it! From a cursory look (all I can find is presentation slides?), it doesn't sound like you'll be able to take any off-the-shelf Haskell subroutines and run them in parallel on the GPU; rather, it's an embedded DSL for constructing shader programs. So I imagine you'd have to learn both CUDA and Obsidian to use it.
But it would be awesome if someone came along and proved me wrong.
Thanks for the read--now, how 'bout another? http://www.cse.unsw.edu.au/~chak/papers/gpugen.pdf, another Haskell-embedded GPU DSL, claims to work at a higher abstraction level than Obsidian, but still provide high performance general-purpose GPU programming capabilities.
* http://www.google.com/search?q=obsidian+haskell