I doscovered the hard way that XSLT 2.0 is not completely backward compatible with XSLT 1.0 and that TS 7.5 forces you to use XLST 2.0 - it's not an option. So if/when you upgrade to any version of TS 7.5 and beyond, prepare to possibly have to update your PTs and anything else you use XSLT for. We happen to use it for all of our email notifications as well. Not all of them need to be updated, but I've found a lot that will not work as is. And the best error message I can find is that there's a transformation error - so you have to figure out what's wrong yourself. Royal PITA.
