Would you expect any less from Google than the gold standard? There are other traffic-analysis programs that can dig deeper and provide more services, but Google Analytics is the market leader because of its combination of function and value. It's free — you can't get a better deal than that.
Google Analytics gets good marks across the board for its basic services. For starters, you can monitor visitor numbers, traffic sources, devices, location, social media shares, conversion rates and visitor flow. There are also plenty of nitty-gritty details available for hard-core analyzers who need to know about things like the screen sizes of their mobile-app users. And of course, the program also ties in with Google's AdWords and AdSense programs.
On the downside, Google Analytics is so complex that learning the full program can be a challenge. Another common complaint is that its real-time stats aren't as responsive as they could be. And some users have expressed uneasiness over the fact that Google isn't collecting all this data solely for the benefit of the user.