Frustrated with xxx:node-set

I want to strike up conversation/thread about the xxx:node-set, if
anyone interested.  I am very frustrated with the lack of consistent
performance I have witnessed using the xxx:node-set function with
MSXML4 Parser.

The node-set function works fine when not used heavily.  When used
heavily there is a potential for problem.  When I say heavy, I mean
using the function multiple times in a multiple pass transformation of
data, maybe wrapping such a process in a template and then using this
template many times to produce different results with different
parameters.

So, in this heavy use scenario, I believe the final kick to the bucket
is the use of a key to perform things like data summing / aggregation
against this produced set of xml.

Your thoughts?
Karl..