I tend to look at humans as being very clever primates, with a lot of the same (though highly adapted) behaviors. We live in social groups and sometimes have to understand and communicate, complex situations rapidly.
If you look on "emotions" as being feedback from our environment, and a way to communicate and understand each other then I think they're are useful. They of course can be misused just as logical thought can be.
I look at them as necessary, as when I look at nature, it appears to be a pretty ruthless thing. Emotions seem to give us an edge in rapidly understanding or feeling something quicker than a logical thought process. We may feel a sense of "fear" and escape a predator long before we logically deduce what triggered the anxiety.
They act as signals, eg when a person cries this usually has a rapid effect on most male humans, lowering their testosterone and aggression levels. Reducing the risks of harmful conflict. It's a complex thing, but if it didn't have advantages I don't think we'd have ever evolved to have them. Just my view.