Good question.First, you can read the files directly just on the SARIT website, of course. SARIT turns the XML into HTML for you.
But if you want to download the XML and use it some different way, the best and easiest converter I know is OxGarage. Select "documents" and then "TEI P5", on the left, and then whatever you want on the right (PDF, HTML, MS Word, LaTeX, epub (Kindle), etc.). It does a pretty good job, and is constantly improving.
One of our plans for SARIT is to build this conversion facility right into the SARIT website, so you can just press a button right there beside the text and take delivery of whatever format you want. It is likely to be handled by OxGarage, which offers a RESTful service (i.e., it can be used in the background by other websites).