Well, the first unit turned on, but didn't do much more than that. The box was attractive and well packed - from a packaging perspective it inspired confidence. But it didn't work. I could force it to manually switch between displays by turning one display off, the other on, and then unplugging/replugging the switch - not exactly what it is supposed to do.
I called monoprice's customer service line and got a live human being within three rings who apologized and sent out a new unit right away. At no point did I reveal any industry/blogging credentials, and this is a company that is selling a product roughly 1/4 the price of the competition, so top notch service is really extraordinary.
The replacement unit worked the first time out of the box. The remote control is ugly and does not have a powerful IR emitter, but it has eight discrete buttons for every switching contingency (Input 1 to Output A, Input 2 to Output A, Input 3 to Output A, Input 4 to Output A, Input 1 to Output B, Input 2 to Output B, Input 3 to Output B, Input 4 to Output B). This makes programming a universal remote child's play, or at least it would have if the Logitech Harmony 880 worked properly with the monoprice codes. After downloading and redownloading and creating my own codes from scratch, I still couldn't get the Harmony to finish the update/synchronization process. Eventually, I gave up and emailed Logitech. Here, too, customer service saved the day: within two days of my email to Logitech's Harmony folks, they figured out and resolved whatever was the problem was and sent me a note to "try it again now." Problem solved.
In three months of use, I have had no significant issues with the second monoprice unit. I have noticed, however, that on its own site, monoprice does seem to have generated a lot of complaints about dead or incompatible HDMI switching units, and this particular swtich has been refreshed several times; it is now up to version "2.5." Some of this is undoubtedly due to the inherent iffyness (a technical term) of HDMI implementations across a wide range of products. Still, custom installers can be forgiven if they choose to steer clear of the monoprice unit and stick with a proven brand like Gefen as their default. For DIY'ers, though, the monoprice unit is an easy recommendation: its price is insanely low, and monoprice is providing quick service should you have any problems. Even if there is an unusually high failure rate for these units out of the box, it is a gamble worth taking.