While being in a search engine index does not guarantee rankings, it is the first step. SEOs regularly use the Google cache command “cache:http://www.yoursite.com” to determine when a page is in the index and the last spider crawl time.
Now, Matt Cutts confirms that Google’s AdSense mediapartners bot is not only targeting ads for AdSense but is also indexing for the regular Google search database, in an apparent bandwidth saving move.
According to Matt, there is no advantage to site indexing by one bot or the other. Those cloaking content and serving different pages to each bot could run into problems in the search index. He emphasizes:
… pages with AdSense will not be indexed more frequently. It’s literally just a crawl cache, so if e.g. our news crawl fetched a page and then Googlebot wanted the same page, we’d retrieve the page from the crawl cache. But there’s no boost at all in rankings if you’re in AdSense or Google News. You don’t get any more pages crawled either.
So, for those sites having trouble getting indexed, is this really a faster way to get indexed? The answer is not clear at this point. I’ll definitely be testing this out though.