Chances are, if you’ve got a website, then you have some kind of analytics installed. If not, you should. How are you going to tell where your traffic is coming from and how much of it you are getting?
You’ve also likely heard by now that Google Analytics is free. Indeed it is. Totally. And you can use it to gather all sorts of useful information about your site visitors. But is it enough? Can you survive on Google Analytics alone?
I think for new websites Google Analytics is enough. You really want to see how your site grows over time. But as your website grows and you take on more search traffic from a variety of sources, you probably want to use an alternate analytics services to compare your metrics.
I’m not saying you should replace Google Analytics. You can keep it installed. There’s nothing wrong with it as a service. But there’s no perfect metrics package.
The point really is that you want to corroborate your data, especially the actionable data. By comparing the numbers you get from two or more analytics sources, you ensure that you are getting accurate data. It’s actually more actionable when you can get reports and actionable data from more than one source. Wild fluctuations between the two can be analyzed and judged according to reality and your expectations.
Google Analytics is good, but I wouldn’t rely on it completely forever. Your SEO is more important than that.