Depends what you mean? If you want a modern high performance ray tracer with support for all the latest hardware and implementing all the cutting edge ray tracing research, there is Embree and OptiX. They don't however come with their own scene description language, which is what made POV-Ray so popular in the first place.
Nothing, except it's thousands (literally) of times slower than alternatives because it uses primitives instead of meshes and therefore doesn't lend itself well to GPU parallelization
