I love that it's free! And you can easily integrate with your website or CMS if needed (Wordpress).
It has some great features but sometimes takes time to load when using mobile devices especially in areas of high traffic/popularity where there are more people online looking around as well. The best part about this tool? You get so many different ways to use them depending what type of user experience you want - from basic stats tracking all over their dashboard up through advanced reporting options via API integration into 3rd party platforms such as Mailchimp etc.