I've had problems with ZA as well but I still think it's a reasonable product (for free) and easy to use for most users. It's also one of the easiest to find help for just because it is so popular.
So 'Fine' here would be not bad/ok/reasonable rather then 'very high grade'.
It has problems with Avast which is another product I often recommend but Avast recognises ZA and presents a solution. I've used the two togethner for a couple of years with few problems.