How do you measure your SEO success?

Each SEO professional has his/her own strategy to get and keep clients on top of the market, whether he/she works independent or for a company.

However, it seems like some SEO Experts become more "successful" than others, maybe for their reputation as professional or simply the company they work for. That's why I have always asked myself about what really makes an SEO expert "successful":

Is it the top positions obtained?
Is it the top quality links obtained?
Is it the Google PR obtained?

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Search Engine Optimization|Web Design Orlando