Never no problem until something gets onto the system and things don't run too well afterwards. With AVG totally disabled from autostarting along with Windows it suddenly popped up a flashing alert when a trojan downloader was copied onto the system upon reaching a new site. When the trojan tried to execute a certain code AVG caught that immediately.
AdAware and Ewido combined detect and remove "data miners" that are used by various sites to track your internet browing habits. The best defense as it seems often proves to be the best offense against adwares, spywares, viruses, and other forms of malwares. Cleaning a system after an infection of one or another can often mean a total wipe of the one or more hard drives.