From the recent SMX East conference Barry Schwartz, contributor at Search Engine Land, confirmed with Steve Tullis, Sr Program Manager Lead at Bing/Microsoft, that Bing does indeed use click through rate (CTR) as one of the many factors in their Bing ranking algorithm. Steve Tullis made the comment that if a search result does not get clicked on Bing will likely lower the site's ranking.
What can influence a user to click on your listing within the search engine result pages (SERPs)?
One of the big influencer is the actual snippet being displayed. If the snippet matches the user's expectation (i.e. the keyword being searched) it is more likely to influence the CTR.
Where does this snippet get pulled from?
Typically a search engine will pull in the meta description tag and use it as the page snippet to display within the SERPs. But the search engines could also pull in a snippet from the actual content within the page. The search engines try to pull in the most relevant snippet based on the search phrase.
The recommended length for the meta description tag in Bing is 150 characters (including spaces). Within that 150 characters you should try to be informative, descriptive, concise, and use your targeted keywords. Using targeted keywords in the meta description tag will not influence search engine rankings, but the keywords will get highlighted in the snippet and make the listing more visible in the SERPs.