No, SystemWorks rocks. Disable the crash guard, which is a piece of crap. The rest is fantastic... you get the newest version of Antivirus (which costs more than this anyway), disk doctor (which has saved my ass dozens of times), windows doctor (which fixed several bizarre windows problems i could never pin down), and a bunch of other utilities you may or may not use.
Just don't enable all the monitoring tools, and you won't see ANY system degradation at all.
NOTE that if you read the fine print on the rebate, it's for users of previous versions of Norton products... be careful.