All people have their own opinions on utilities, A/V, antimalware, and other software... and here is mine.
I use Iolo System Mechanic (not the Total Care, as I use other A/V and Antimalware).
I have used it ever since they started up.
If used correctly it does what it says it does.
Basically, it does everything you can do manually; however, for those who want quick and tire of hunting for the options to do these tasks, it works great.
The guys/gals there get back to you in 24 to 48 hours and handle your problem, if need be... they don't go the reset or re-install route... they actually try to figure out the problem.
In my opinion, those who think they will never get bitten by a virus, drive-by, Trojan or one of the hundreds of thousands baddies... good for you.
But for the rest that know these things are out there; and, the people that use them are trying everyday to find a way to infect you for their gain.
I use A/V and Antimalware apps and have had them stop many attempts... would the attempt have gotten through without them, possibly not, but I don't have to worry about it.
Please, use your firewall, A/V software, Anti-malware... if it slows you down... might be time to upgrade or figure out why and fix the problem.
Modern PCs system should be more than able to handle the apps; and, a firewall is a no-brainer.