Thanks for the response.
The rich snippet testing tool has actually been available for a long time, but they've recently made improvements and created a menu category for it (it was previously in the labs/beta section). However, the tool doesn't actually predict the snippets you get in search results, it just verifies the semantic markup and shows an example of what your snippet might look like. At least that's been my experience with it, and I've heard the same from other people around the industry.
Ideally Power Reviews/Bazaar should just update their markup to Schema.org format. Since that's the preferred format agreed upon by the powers that be, I don't understand why they wouldn't, unless their framework is just extremely rigid.
I appreciate your feedback about your client sites running PR. If I understand the (limited) documentation correctly, this shouldn't be a problem unless I was marking up the exact same data with two different formats. Just wanted to see if anyone else had direct experience. So thanks