They disabled stagefright because it sucks at AAC HE.
Yes, but I'm realizing now that there are quite a few streaming apps that require stagefright, notably WinAmp's shoutcast support. The app says these features only work in 2.2, which we have, because when coding with APIs for Froyo, it is assumed to be there. Leaving it in might break some legacy support, but taking it out breaks others. Its a lose-lose, really (which may be why many manufacturers have been taking their sweet time with Froyo updates).
Since the device sells with 2.2, I can imagine many users scratching their had as to why media apps made for 2.2 don't work!
I think there's another reason it is disabled, and either way it doesn't explain why no JIT.