Sharpness
The gallery above has a variety of images from three resolutions - two 1080i images of NFL football (one GameMix) off of DirecTV.
Next is a pic of Katniss, and then a close cropped version of the same frame. The remainder are 4K images, a full frame, and a close cropped version. The close cropped versions are saved as 2000 pixels wide to show you the full detail possible (since we are looking at 2000 pixels across only a small part of the 4000 pixel wide frame.
Sharpness and detail are excellent. Based on previously comparing the more expensive but similarly sharp VW665ES against a JVC with pixel shifting, the Sony should easily surpass the JVC overall on 4K content. When it comes to very fine lines, the Sony will be very visibly superior, since each pixel is 1/4th the size.
Epson's LS10000 and their new 5040UB/6040UB models are more 1080p pixel shifters like the JVCs, but the Epson's give the Sony a closer contest. On 1080p content, the Epsons will often seem sharper and crisper, but that's due to some very heavy image processing, and the Epsons in turn will provide a slightly "harder" looking image, which if you look closely you'll fairly easily spot in closeups of faces. On true 4K content, the Epson again, seems very sharp, but it really cannot match a true 4K projector, especially on the finest detail, because again, each pixel is 4x the size of a true 1080p pixel. On a fine one pixel wide line, there's absolutely no contest. Still on normal movie content, it is curious that the Epson at a glance seems as sharp. I like the pixel shifters, especially the Epson's for their perceived sharpness and detail to the entire picture, but it simply isn't as natural, and obviously can't deliver the finest details to rival a true 4K like this Sony. I've included an close-up of the same computer screen from Enders game from an Epson pixel shifter for your consideration.