I suppose it depends on your background. I use other languages that chain
equal-precedence operators in this fashion. Perl's logical OR operator comes
to mind first - "$a or $b or $c", with short-circuiting evaluation. Python has
a similar short-circuiting OR operator.

Although I'm an XSLT novice, so perhaps if my brain were steeped more in XSLT,
its nuances would render this less obvious to me?

 - Chris