Forget about Cocoon, and caching. XSLT is really really fast. Both MSXML4 and LibXSLT are simply incredible performance-wise, even if you parse every time. But then I guess we really need to do some sort of proper benchmarking to prove that :-)

(not with AxKit though - it's internals are large, and would hide any performance difference against other solutions - what you should look at is a pure TT solution vs a pure LibXSLT solution, or something. I wish I had time to do the benchmark :-)