There is something like 2,700 replies to this discussion over at AVS. While I'm not a huge fan of digging through the nitpicks there, it still really has the best personal ownership observations of many specific models of projectors.
That said, I am a huge JVC fan. For years they have delivered a robust product which not only holds up well, but blows the competition away in terms of contrast. The image quality of their units is similar to many others... That is, good color, good sharpness. Their brightness on newer models is improved from prior years which allows for larger screens, yet they still maintain industry leading contrast.
Their 4th generation of eShift 4k technology may not stand out as exceptional compared to native 4k, but offers an improvement over 1080p, and this is no longer new to them. They aren't just 'getting into' the 4k market, but have been doing this for many years now. This all helps to increase and ensure stability and reliability if you are planning on using 4k sources.
I believe this is also the RS400 on their professional side, which should be identical to the X550. So, you may find some more options online for that model and perhaps at a better price.
I'm not going to link to the AVSForum discussion, but would strongly recommend you go find it and check it out.
