XFI Advanced Security question

Now I realize this is Xfinity help forum and therefore knocking xfinity products may not be very popular but question is do I really need XFI advanced security? This used to be a paid service and I never had it so now that its free what happens if I disable it? Will I really be completely unprotected, what I'm really getting at, how much do I really need it? I read thing that it blocks legit sites and causes problems with devices. 

EG I would love your input on this one.