Lately, I\'ve been pondering the somewhat non-mainstream architecture of building raw XML on the server side, and then using an XSLT stylesheet on the client to transform the XM
I don't know any big public Websites that use client-side XSLT transform (well, except World of Warcraft mentioned by Joel :-). So I cannot answer your question directly.
However, from time to time I was pondering the same question myself, and I have a hypothesis that the number of such sites on Internet must be very close to zero. :-)
The short version of my theory behind this hypothesis is this: with the exception of some pretty exotic cases, provision of client-side XSLT option is simply not worth the trouble. :-)