It seems that Bing have dipped their toes into using Rich Snippets. Bigdude said this was important some months ago on this forum.
The format is the normal three line entry followed by a fourth line derived from Rich Snippets.
For the sector I'm looking at the fourth line reads:
User Rating 4 5/5 . 8 reviews
Looking at a search of widgets, this only first appears on the third page. I suspect this may be because there are various formats of Rich Snippets and I think Bing has adopted only the latest which is prefixed by:
I hope so because that's the one I've implemented on my site. I suspect other Rich Snippets are being ignored by Bing. That's why their appearance is so rare at the moment.
I can't confirm this because I've implemented some features of that version of Rich Snippets but not yet the rating one. I'll do that asap on a few pages and see what happens.
Rich Snippets will get more imortant in the SERPS. And to the dissenters, remember this, you only need to declare the information you want to declare, If it's incomplete and unusable the Search engines wont know. Let them think they are harvesting good information form your site when in fact they are harvesting incomplete and unusable information. What they harvest via Rich Snippets is in your hands.