Hello Dan,
I like the idea of a more user friendly citing extension. However, a few points:
1- AJAX... Sweet, nice, and all that. Completely unusable if you have javascript turned off, or if you're using keyboard only to navigate, or use a screenreader. Not saying not to use it, but provide a non-AJAX alternative. Accessibility and usability are important.
2- Don't assume that everyone who would use the extension has access to PubMed.
3- Don't assume that all articles are available through PubMed. I've access to PubMed myself, but many research articles I am routinely hunting for aren't available, nor referenced, on that system,
So, there you go, my 2 devaluated cents ;)
Good luck and happy hunting
Sean