The diacritical support of Charis SIL is definitely a major selling point. Much of what I read has no need for such extensive support, however, so I've gone for a little more flavor. Charis SIL is definitely an excellently designed font; just not to my liking. I'm still a huge fan of
Iowan Old Style for most of my reading. Unfortunately that's also a paid font; guess my experience in typographic design makes me a little too picky for my own good...