The downside is, of course, the wildly varying style and quality, which means that finding the good images can require sifting through lower-quality content. But at least to me, that's often more useful than a comparatively tiny selection of consistently high quality art which probably just isn't going to have what I'm looking for. They also are using straightforward CC0 terms, which is always a plus compared to custom licenses.
The downside is, of course, the wildly varying style and quality, which means that finding the good images can require sifting through lower-quality content. But at least to me, that's often more useful than a comparatively tiny selection of consistently high quality art which probably just isn't going to have what I'm looking for. They also are using straightforward CC0 terms, which is always a plus compared to custom licenses.