Brief review after a couple days now with mine:
I moved to this from a DYI masking system. I liked the masks I made but in the end they didn't hold up well and were just a pain to put on/take off.
However I found I really liked having masks - they make a huge difference. And the screen I was using them with, an Elite bright white, while ok wasn't that great - I had a Carada years ago that was too big for my room but much better - so I was faced with either buying a better screen and coming up with a more permanent DYI masking solution, buying this, or dropping several grand on a Carada or other similar electric solution. From various reviews over the last couple of years I knew the screen quality of the Monoprice would be good - and it is - so I went with this one.
Installation as mentioned was a pain in the rear thanks to near-useless instructions. After figuring out how the masking plugs worked per my post above the next step was puzzling through the mount, which is...different. Also, the least-well documented step in an already bad manual.
At the end of the day, the brackets go up with the piece that has the "shelf" on the bottom - even though it hangs off straps make sure it is squared and leveled off and measure the distance between brackets or you will never get this thing to hang straight. Next part was figuring out the clips - I didn't get them at first, because it looked like they would make the screen stand off from the wall, and it's already a thick frame. And they do - that is the right way to assemble it. So fair warning, if you are really sensitive to screen distance in your room this screen will easily subtract about another 2.5 inches or so from more "typical" flush wall mounts.
On the plus side it is, when you finally get it together, a really solid mount (it has to be, the entire thing is quite heavy). And the stand off contributes to a "shadow box" effect which I quite like, actually. Also there's plenty of room to put LED strips on the back to reflect off the wall if you are in to backlighting - I do this with my TVs, it makes viewing in a dark room much nicer, so I am on the hunt for a kit that is long enough for this screen. Finally, it's pretty easy to slide back and forth for horizontal adjustments - probably a lot easier than doing it on your PJ (the screen comes with locking nuts to prevent it from being moved when you are done, but I don't see the need for them - it would be pretty hard to accidentally move this thing and even harder to knock it off the top and bottom brackets).
The screen frame is nicely wrapped in black velvet and looks good, though I see the same slight peeling on the bottom AMartin56 did - it was easy to tack back down, but slightly annoying. It's a wide frame all around with beveled edges similar to the Carada Criterion series. The width and bevels really contribute to the overall look and contrast pop.
The screen itself (I got the bright white) is as I hoped a step up from the cheap Elite I had - which isn't saying much - and to my memory anyway is on par with my old Carada brilliant white. It gets the job done. Attaching it to the frame is done via tension bars and spring clips, which was a little bit of a pain but keeps the surface nice and smooth.
And, of course, the masks. It's why you are buying this right? They are tricky to work at first; you have to pull all the way up on the bottom to get it to drop right, otherwise it won't retract (the top always retracts fine). It's one of those things where once you do it correctly a few times you'll figure it out - at least this is what I am hoping after two days, so far so good. The advantage to this is when pulling it up, as others have pointed out, you can get to to stop wherever you need, so it's good for more than 2:35:1.
I think I might have a newer model because my bottom mask has two fingerholes (most of the pictures I have seen show one) and unlike some videos I have seen I never have to pull the top down at the same time, all I need to do is smoothly pull the bottom one and both masks expand/retract. Maybe I got lucky in having to install the thing a couple times and got pulley system right - though that part comes pre-assembled from the looks of it it'd be easy to mess up or get the wires to accidentally catch on something. Also I spent a lot of time making sure both the frame and the mount were completely level and squared off - the way this thing operates, if you aren't completely square I would bet you'd have trouble with the masking. Measure diagnally and don't be shy about taking the thing down and fixing it if it isn't completely square (I also did the mounting brackets twice - hint, make sure you drill in screws on the extreme ends of both, then put a couple towards the middle, 4 in all for both the top and bottom bracket - the instructions only show three each, and I think are generally very unclear on this point).
Finally, make sure you level the mounting clips when you screw those in to the frame as well. They are not even mentioned, and barely shown, in the manual btw. I mean, not even listed in the parts section. Come on Monoprice.
Still, after everything, I am pretty happy with it. The price was great (I got it at the current holiday discount, which is still going on I think), the screen itself is very good and the masks do exactly what I hoped. One day maybe I'll go CH, but that will take a move as my current house/media room isn't really wide enough for the screen I'd want. In the meantime this gets it done.