Firefox gets heavy and slow, even slower than BF3 at full settings if you browsed for more than 5 hours consecutively.
Opera is not good for office uses, they cannot run MySAP, ERP applets, and other web-based application interfaces, to the point it is frustrating, because when you see Google Chrome runs them well, you started to all rage.
Chrome on the other hand, automatically downloads and installs unwarranted programs without warning or notification.
I have all 3 of them, and also IE9, to run apparently fascist corporate HR/ERP/Reporting apps, because they seem not to accept anything else besides IE.