The JVC's have never been among the very sharpest looking 1080p projectors around, nonetheless, it isn't a serious issue. I refer to the JVC projectors as having average sharpness, simply because they do look sharp. Any differences on movie viewing between the RS20, and the sharpest images out there is slight. Where you might notice a bit more difference is with a straight digital video signal, as you don't have the softening effects of the film, that comes with movies.
Perhaps this average "sharpness" is due to JVC's use of LCoS panels which have the least visible pixel structure. That may inherently make them look a little softer, even as they reveal the same amount of detail. That wouldn't surprise me, as the Sony's are typically similar to the JVC's and they too are LCoS. The other major projector that tends to fit in the group (in terms of sharpness) is the Panasonic PT-AE3000 which uses their SmoothScreen Technology on their LCD panels to end up with a pixel structure no more visible than LCoS.
I don't notice any huge differences between the RS20 and the sharpest 1080p projector I have here the InFocus IN83 when watching movies, but I can definitely spot a little softening on my HDTV sports viewing. (I sit close, and have 20/15 corrected eyesight). On the other hand, side by side you can see, for example that the IN83 is sharper. The JVC does have a nice sharpness control and a detail enhancement one as well, on the advanced Picture menu. You can dial them up quite a bit, and get more sharpness, but if too far, you'll start getting some sharpening artifacts. The RS20 sharpness images taken below were the default sharpness settings. Dialed up, the sharpness and detail enhancement bring the JVC closer still, to the IN83.