A golden article about Gentium:
http://www.lisa.org/archive_domain/newsletters/2003/4.3/gaultney.html
My favorite part*:
"For example, the Latin �o� and Greek �omicron� share the same nominal shape. I found, however, that due to the nature of the Greek alphabet, and the combinations of letters that included the omicron, that I needed to change the shape for the Greek."
* Well, maybe my second-favorite. You can guess the first. :-)
hhp