The Sony is indeed a good choice for its type. It does not have phase detection AF, but its contrast detection AF is reportedly very fast. You can make it even faster by using technique of pre-focusing, or holding down the shutter button half-way to engage the auto-focus and exposure before taking the photo.
Some newer non-DSLR cameras offer phase detection AF in addition to contrast detection AF. The Nikon 1 cameras have such technology. Nikon 1 cameras use the same size sensor as the RX100, but the Nikons are interchangeable lens cameras. The upside of that is you can attach an appropriate lens for low light, landscape, macro, etc. The downsides are you can't have an all-in-one lens, and the whole package is physically larger.