I like this project a lot (and use it ocassionally in my PhD). I've tried this full profile Rietveld-esque tool [0] before, and it works pretty well for being so simple (at least from a UX point of view).
What I would like to see (and would program myself if I was a better programmer and knew more of the math and physics behind XRD) is a libre search-and-match program, using a peak database (in reality, multiple databases for different X-ray sources) constructed from the CIF files in COD.