What are the benefits? Combining the two streams, you get real optical zoom with full resolution photos. So if you have 13MP sensors, the final image is 13MP even if the zoom was used. In our case, the lens had up to 3x zoom in in 13MP photo mode and up to 5x in 1080p video mode. You should also get better detail and less noise, as you actually have twice the image sensor area compared to a single sensor. Focus speed can also be better, as the processor can use data captured by both sensors and calculate the distance to an object instead of only relying on traditional contrast detection technology. By calculating the distance to objects, augmented reality can also be improved.
The drawbacks? Of course, it is slightly bigger than just a single camera. The prototype we saw was about 6.5mm deep, so if you have to integrate it in a phone, it can't be the thinnest one without having a camera bulge. It was interesting for us to see this new technology, and whenever it is available in a commercial phone, we'd be happy to test it out.
reference: Core Photonics