It's a fairly robust, infrastructure-type monitoring. It gives you a framework and lets you implement custom code, which can work well. It has some pretty good documentation, although not all aspects are as well done as I would like. It’s also extensible.
Because it generally meets our needs on the whole, I’m fairly satisfied.
We have a fairly big IT department with different teams being on different calls. We use OpenView to watch databases, apps, Windows servers, and node servers. Even though it’s not monitoring application health directly, it still sends notifications to let teams know what's happening.
It just makes it possible for the on-call tech to relax and wait for stuff to notify them of problems instead of having to, over the weekend, constantly sign in. It babysits for them, when we code it right.