Google's 18-year history has been filled with more successes than failures. A few services, however, are lesser known or have been renamed completely since their inception such as "Google Answers" or "Froogle". Chrome OS is one example where its success or failure has been difficult to measure since Google is relatively silent on both direct sales numbers and market penetration of its Chromebook family.
Market analysts at IDC have estimated that systems sporting Chrome OS have outsold Mac OS systems in North America for the first time ever. As of Q1 2016, the combined sales of Chromebooks from Dell, HP, and Lenovo have reached nearly two million compared to "only" 1.76 million MacBooks, iMacs, Mac Minis, and Mac Pros during the same period. The study does not take into account iPhones or iPads, which all run on iOS.
Much of the success of Chrome OS can probably be attributed to its use in educational institutions. Nonetheless, the popularity of Chromebooks likely remains lukewarm or else Google would be boasting sales numbers left and right instead of relying on external analytical firms. The company will soon allow Android apps to run natively on Chrome OS, which should increase the versatility of Chromebooks and boost sales at the same time.