Live.com Shopping launched today (official blog post), and all I see is a big message saying they don't support Firefox. It doesn't work with Safari or Opera either (same Firefox error message for all non IE browsers). The entire Mac audience has been shut out of Live Shopping. I'll fire up my Windows machine to test it out later.
In general, Microsoft has been good about supporting Firefox for its new live.com products. Live Shopping should have been delayed until it supported Firefox, too. Most bloggers and journalists use a Mac and/or Firefox and this audience was just completely alienated from Live Shopping.
Ian McAllister, the Program Manager for Windows Live Shopping, has more.
Just as a point of interest, here is today's browser breakdown for TechCrunch: