Very subpar review. The author got a free to review projector and proceeds to listing the specs and some marketing blurb without doing any proper research.
I actually do own one of these UST's(different brand) and the special screen is a must. It "only" costs about 800 Euros on aliexpress.one cannot stress enough how much of a difference the screen makes. Either way a quick youtube search would bring up lots of proper reviews of the xgimi as well as side by side with or without screen of various UST projectors.
Non of them are really cheap but if you want a true cinema experience then it is worth the money.
Either way I suggest the author uses youtube to see what a proper review actually looks like and how the projector should be set-up.

Inexpensive my A S S ...

Wish I had a 1% job like working for this  website so that  $2,800 projector was "inexpensive".

$2,800 buys a first rate flat panel tv that would blow this away.

Guessing they gave you one gratis?

Inexpensive projector... Baam almost 3000$! suuure...

The importance of a screen, and a good one, really can't be emphasized enough. I've never used nor seen a UST projector in-person, but I did quite a bit of research a few years ago and was initially leaning that way, until I realized not only are the projectors themselves more expensive than comparable standard projectors, but they are much more dependent on a screen for good image quality, and the screens they require are different from the standard ones and are, again, much more expensive. You can build them yourself for significantly cheaper, but you're still looking at easily a few hundred for just the screen. So it's something to keep in mind before going this route, and UST is probably not a good option if you're not going to get, or build, a good screen, as you'll likely pay more for worse quality.