This thread is sleeping, presumably everybody's having fun with their Sony A7s. Meanwhile, my K-3 has been proving its worth during last week's ski trip to Schladming, Austria. All photos with the new 20-40 limited lens. The lens copes well with the 24PM resolution, its only meaningful fault is fairly significant vignetting that doesn't go away so easily by stopping the lens down but that can of course be fixed in pp (still a bit of a let-down when one comes from the Leica world and expects lenses to be close to "perfect").
In response to 4711 above - re colour accuracy, it is whatever you set the camera to; there are so many settings possible in camera that this question is almost impossible to answer. For example, you can set the response to "reversal film", then the images come from the camera accordingly. When I leave the camera on Auto WB, it is usually fine but in certain situations (kids skiing in overcast weather, for instance) it sometimes needs a bit of help in pp. AF speed is fine, accuracy also, but children are a specific and difficult subject - I find the Olympus EM-1 or EM-5 faster, due to their face recognition / focus on nearest eye feature (this is of course possible only in Live View, so best implemented in an EVF type of camera; here the K-3 does live view but focusing in it is not as fast as in the Olympus cameras). As for the tele zooms, I don't have the answer but can vouch for the F*300/4.5 which is super sharp even wide open, and is small and compact. I have the FA 35/2; it can handle the 24MP sensor but, owing to the crop factor, that's not what 4711 is asking. I tried the FA*24/2 (which would be the equivalent of 35mm in FF) but I don't think it cuts it in the modern age, unfortunately - good contrast and lovely colours, but resolution is not there, especially wide open and even 1 stop from wide; also has quite a bit of purple fringing.