There's a huge gap between "not especially efficient" and "violates all kinds of standards" -- and I have verified that Java (or Limewire, at least) does indeed violate standards, namely that a lower priority task is not supposed to preempt a higher priority task under a true multitasking kernel (such as the NT kerel in XP, and any unix whatsoever -- in other words, nearly every modern computer, including home computers).

Yep -- a Limewire "niced" to BelowNormal priority makes tasks with AboveNormal priority stutter on my own XP rig, despite there being enough RAM for both tasks and the tasks not having to time share any other device (e.g. network, hdd). No swapping, no significant drive activity, but task manager shows the CPU usage swing massively in favor of Limewire every so often, and I guarantee the other task is not yielding the CPU voluntarily or blocking on anything!

Why does it do this? This is like the bad old days of 16-bit Windows 3.1 crap!