The best option is to run all three, just to be sure that you catch every piece of spyware on your system. Afterall, no program is perfect. In addition, its real-time scanner adds a type of protection not found in Adaware (unless you purchase the full version).
You need to weigh the value of the system resources it's using versus the benefit it has provided. For me it has barely put a dent in my system resources (even during a full scan), and in return caught numerous more spyware installations than Adaware and Spybot combined. Personally, I'd recommend keeping it installed. However, if it has not caught much spyware, and you feel the other programs have provided sufficient protection, it may be best to uninstall it and apply the system resources towards something else.
Hope this helps,
It slows down my computer and never finds any spyware that ad aware and spybot do. Should I keep it for the real time agents or dump it?