I would urge caution - as with everything else with Google.
About 8 months ago I went through a lot of sites that were reasonably successful - page 1 positions for decent search terms - but they needed to notch up a few more places in order to make real money. I got a list of synonyms for the main search terms and re-wrote them using these, with no one word mentioned more than 6 times in a 500 word article and the words mixed up to ensure that the same phrase was not repeated more than twice. I made sure that the English looked good and easy to read with none of the 'spun content' feel that so many other sites have. One site rose a single place in the SERPs, the rest disappeared down to page two or worse.
Two months ago I re-did the graphics on all these sites to try to make them more attractive and professional-looking. Many of them have since risen back to page 1 for the target terms but two previously very successful sites have bombed.
My conclusion? I haven't got one apart from the knowledge that Google's algo is highly complex and what may push one site up can just as easily send another down and, leading on from that, that there are other factors at play that I do not know enough about at present.