Take a page, form, whatever, that is relatively long to load, say:
During the wait, there is no busy cursor.
There should be, IMO.
You'll get a "Waiting", on the (what was) status bar, bottom left, which you're not likely to see.
You'll get the "bouncing balls" in the tab, which you're not likely to see.
As it is, on a slow, long loading page, quite often I'll find myself in a "what's going on here" situation, not realizing that something is still happening - because there is no obvious (or at least too obvious) indication that something is actually happening.
A busy cursor would provide that feedback.
(For that matter, to clue me in, I'd actually take the page going opaque ;-).)