I/O prioritization noticeable?

Hi,
internal notebook drives aren't particularly fast. While copying files
from a faster FireWire disk, my old MacOS 10.4 becomes unusable,
launching a small application will take minutes. Burning a DVD at 8x in
the background already thwarts watching high-bitrate video.

I've read that Windows Vista introduced I/O prioritization to address
exactly those problems. Does it work?

The benchmarks I found didn't include cases like the above.

--
Tobias Weber