May I add the very appealing unlimited uses.

Unlimited? Heh, you obviously only read the front-page blurb and not the terms of use which has many different kinds of limitations including that Bing can slip ads into the search results and you're not allowed to interfere with the display of them:

http://www.bing.com/developers/tou.aspx

If you want "unlimited", you'll get much closer by using Yahoo's Search Boss API. Roughly the first 10,000 queries per website are free, and there's a small charge after that. Because it's a commercial service, they don't need to put in all the restrictions that the Google and Microsoft APIs have:

http://developer.yahoo.com/search/boss/