OS/2 seems to be quite good at dynamically shifting process/thread priority on the fly so UI code isn't adversely impacted.

It isn't as obvious on newer hardware, but on ancient machines like the ones I still tend to run it's sometimes apparent that some other OSes (Win2k, Linux) are not quite as nimble at shuffling their feet under load.

Scott G is still making OS/2 kernel patches available -- it'd be interesting to see if his activity continues past the drop-dead date.