Carl, I believe there are quite a few geologists who have never encountered stable-isotope techniques, though everyone knows about radioactive isotopes. (Very often when I tell people that i work on isotopes they think I am doing dating. Not at all.)
I think I may have heard of the blood vessel work but I had quite forgotten it. Obviously very good work and highly indicative but it doesn't produce a number.
Of course diagenetic alteration of material has to be considered and most material will not be suitable exactly for that reason. I've worked on recent (ie late Pleistocene) bone and, quite apart from any checks done outside my lab, we always measure the C:N ratio to check for diagenesis. Even the person working on corals only 5ka old checks for alteration of the aragonite to calcite. She used to just use XRD but has found thin sections to be more sensitive, even though it is more work and the section maker really 'loves' such soft porous material ("Hey Jose, at least it isn't a soil").
BTW did you hear about the Ichthyosaur found in a school vegie patch at Richmond Qld??
http://www.abc.net.au/news/stories/2...26/2909511.htm