Probably looking to target savvier photographers, the approach of this new Pentax is very different than for the Q, with a much larger APS-C sensor and the use of the existing K mount.
The choice of the K mount will make the K-01 compatible with a large range of lenses directly at launch, whereas the Sony NEXs and the Nikon 1 J1 & V1 offered only a very limited number of brand-new lenses at release. But the K mount design requires a large flange focal distance compared to lenses designed especially for hybrid cameras. This said, the K-01 is still very compact when coupled with its 40mm F2.8 kit lens.
Overall, the use of the K mount certainly makes the K-01 slightly larger than it could have been with a specific mount. For example, the K-01 is larger in every dimension than the Sony NEX-7 (also an APS-C): 120 x 67 x 43 mm (NEX-7) vs 121 × 79 × 59mm (K-01).
In term of its sensor, the K-01 features a comfortable APS-C sensor such as that for the Sony NEX series. So we can expect a pretty good image quality, especially if the sensor is as good as the Pentax K5's, one of the best APS-Cs in our rankings. Another similarity with the K5 is the sensor shift stabilization system, which is a premiere for a hybrid APS-C and can help you avoid pushing the ISO setting and creating unpleasant noise in low-light conditions.
One last thing: in terms of usability, the K-01 seems to offer a reasonable number of controls that are directly accessible through buttons and wheels. But the total absence of a viewfinder is potentially a show-stopper for certain serious photographers, who might otherwise have been interested in this camera.
Overall, this new hybrid camera by Pentax seems much better armed than the Pentax Q in term of image quality, and we are really looking forward to getting a production sample in our lab to compare it with its competitors.