You're right Chriss, granular is a kind of timestretch, but it doesn't really stretch the sample, as you said it cuts the sample into pieces and rearrange them. It's not really a synthesis like FM or analog, it's more an audio FX...and you can make good sounds for experimentation...so you won't really produce bass or other sounds with it...or you're very lucky !

I'm on mac and I sometimes use Metasynth or Cecilia for granular stuff.