i don't think google analytics gives accurate results.but compare to other tools it gives better results.
You can't say Google Analytics is 100% accurate, if you want 100% accurate then there are lots of tools but its paid.
you can say it is accurate but not surely about 100% accuracy !! I have monitored it and sometimes it shows wrong results....... !
google analytic is best tool avaialble for traffic estimation but I love Statcounter , google analytic is about 80% accurate
In my opinion, Google analytics gives 100% accurate results. We can see the visitor behavior and also Traffic reports and sources in less time and periodically. Jyoti ABCPune