Certainly interesting. It is good to have a tool something like this one to find the difference between search engine results. When it comes to results, yes, there is a difference in the results you will find for each keyword in different search engines. The reason is ofcourse, algorithms of the search engines
Sometimes, you will also find that the search results are almost similar in different search engines which is good for the websites rankings on top of the search results on each search engine
The results for images is also a good way to find out the relevancy of the search engine. Hence, generally, I do that to find out what kind of search engine it is

As far I think, Google has been the best till now but Bing is catching up faster and hence I waiting for it. When it comes to Yahoo search engine, I do not even try to use it ;)