Be aware that ambient light rejecting (ALR) short throw or UST screens are prohibitively expensive, but you are under no obligation to use such a screen if your room doesn't need it.
I've seen a couple of comments about the cost of UST screens, and it's only applicable if you need a ALR screen.
If your room is good, then any standard high diffusion screen will work just fine and is all that you need to be using. It is the standard practice for most decent home theater setups to use a minimal gain white screen, and that is just fine for short throw or ultra-short throw projectors.
At this point, I'm still unaware of any sub $3K models coming to the market from any manufacturer and I'm completely blown away that Dell is the only one who has stepped up to the plate with a realistic UST 4K solution.
But, at $5,000, we would be talking about that in the other forum I suppose.
Optoma and BenQ really have been the kings in that department for years with their DLP models used all the time for quality large screen setups in a tight space environment. Hopefully we will see them at least announced by the end of Summer.
I think the big key is that they need to get the lensing correct on short throw models. They are much more difficult to make than standard throw models and that is why even the newer models tend not to have the same throw that the old W1070 models used to deliver.
As throw distance gets longer, the lens is easier to make and the image is generally sharper and more accurate/uniform. As it gets shorter, the steep projection angle and significant difference between top of screen and bottom of screen projection gets incredibly difficult to accurately project without image distortion and with no loss of focus.
Short throw is always a compromise. UST is even more of a compromise. But, it can still produce a solid image if designed and setup properly.