I like that it was easy for me as an admin user with no technical skills, to add my own domain names so we could track who visited our site without having them contact us first! It also provided great data about what content people were searching for when they came through from different sources such as google or other websites.
Sometimes there can be issues where certain browsers don't always show up correctly in some of their reports - this isn't too big of an issue unless its something specific that needs fixing though. We've been able to see how much traffic comes directly from Google searches versus others and have found out things such as if someone searched one word vs another related term etc.