Version 3.0.13 of the Top and Latest Review modules has been released. They now support reviews with no ratings.
Since version 3.0.0 Simple Review has supported the hReview microformat in the default template.
The below image is a real-life example of a Simple Review review appearing in Google search results (you can Google “kool keith drugs review sardless” to see for yourself)
Google, Microsoft, and Yahoo! have teamed up to created http://www.schema.org/ so that their new review formats (and others) will be supported amongst their search engines. The current hReview format will still work, but if you are keen you can upgrade your review templates to support the schema.org ones.