It offers the least access to major search engines and a relatively high use of paid listings. More details about each of these services can be found on the Meta Search Players page. When selecting a meta search service, look for one that gives you access to the largest number of major search engines, as that's the main reason most people use these tools. Then, be sure to adjust the default settings to ensure you are getting back those results. There is nothing wrong with paid listings.
Advertisements have their place at search engines, just as they do at many other media outlets.
However, if you are concerned you cannot recognize the paid listings, message the meta search service and ask for paid links to be clearly identified or placed in their own section of the results page. Finally, keep in mind that the actual relevancy of meta search results obtained was not evaluated in this survey, only where the content was derived from. If your favorite meta search service provides results you find relevant, then by all means, stick with it. However, if you have felt that relevancy has declined over the past year, greater use of paid content might be to blame. Consider exploring other options.