At least initially, Google’s (NSDQ: GOOG) free audience measurement aid, AdPlanner, isn’t likely to represent much of a threat to established services offered by comScore (NSDQ: SCOR) and Nielsen. Several ad agency execs offer their first takes to Mediaweek, and say they find Google AdPlanner sorely lacking. AdPlanner’s promise is based on being able to better target online ads through a combination of audience measurement numbers, search engine data and information from third parties.

-- Not ready for prime time: In his review of Google’s latest tool, David Smith, CEO, Mediasmith, finds that the product’s demographic data isn’t particularly insightful and it doesn’t even have a reach/frequency function. Smith: “It’s absolutely not ready for prime time.” Jim Spanfeller, CEO Forbes.com, simply feels that AdPlanner doesn’t add much to the other existing services. Ultimately, Google’s numbers “are as bad or worse as anybody else’s out there.”

Google might argue that if larger web publishers and ad agencies aren’t impressed, well, it wasn’t just meant for them. Google is mainly aiming AdPlanner at smaller sites to use as an adjunct to its AdSense service. And so, it’s hard to find fault with comScore CEO Magid Abraham’s view that AdPlanner is a cynical ploy to attract more marketers to sites within the AdSense network. But as Michael Winter, media director for Agency.com, said: even if it is meant as a lure to advertisers “the sites still need to perform.”

• Google To Launch Media Planning Tool AdPlanner