I had a pomegranate today

I'm thinking grapefruit now.

It's definitely not that sour. If I were to compare it to something else, I would think of it as a sort of mix between a strawberry and a raspberry in terms of flavor (mostly tangy but mildly sweet). Pomegranate juice can taste sour, though, just because stuff like POM's so concentrated that you're supposed to mix it with something else.