I'm not a big fan of MS products usually. I use Apple and Google software mostly. But I have to admit msn's image search blows the competition away. It has so many cool features, such as:

• Lightbox (called Scratchpad by MS)
• Dynamic resizing of thumbnails
• Details of thumbnail on hover
• Easy refinement of search terms (size, orientation, color, style, face)
• Endlessly scrolling page (like Google Reader)
• You can give msn feedback on the images (not sure how useful this is)

I think all these make image search much faster and easier than doing the same with Google or Yahoo! Congrats MS! :)

Also, check out their video search, the videos start playing in a thumbnail on hover! WOW!