The usefulness of Moz depends on how much time/effort you're putting towards SEO. If SEO isn't a top source of traffic/customers for you, then I'd say don't bother. Otherwise, it's useful mostly for tracking keyword rankings.

(It's too bad they don't have any plans smaller than $99. At that price, I'm constantly wondering whether I'm getting enough use out of it to justify the cost. If it was any lower, say, $49, I wouldn't even second-guess it.)

I've used Moz. It's worth it if you have time and resources to follow the advice that they give. It's not one of those tools that is a fire and forget, because you still have to make the effort when it comes to content marketing or linkbuilding.

Try the free plan of BuzzSumo. It's sufficient for our needs.