I think the best reason to buy the K-S1 is that it comes in a color you really like. I like the Night Skye colorset:
On the techpart:
- It has some futures that are an advantage over the K-50. If you use them. The AA-filter removed may give some crispier images. The bigger viewfinder is an advantage, but I do like the O-ME53 viewfinder enlarger to get it better. I had it in my hands at Photokina and it did feel good in my hands, compared it with my K-01. I think that holding a camera is also something that grows in your hands. In many other ways it has a lot of the K-50 inside wich is similar to the K-30. So at least it is a good camera in that point.
- The new sensor should be equal to the 16mp sensor used in K-01/K-30/K-50 so that should be good.
The wheel on the back of the camera looked good to me. I can get used to such a thing. Different then the wheel on top of the camera like we are used to, but also much better then what Sony does with Nex when you only have a wheel on your screen and no fysical wheel.
On the price it is almost equal to the K-5 II at the moment overhere and I do think that is to expensive (for me). On the otherhand that is a total different camera.