The SDC Megtron LCD is most definitely a very useful device. After using it for over two weeks now, I would not want to go without it. The fact that it displays all types of vital information while the main screen is filled with different applications is invaluable. When you are watching a movie in full screen or playing a game, you will still have an eye on the time, on the CPU utilization, how much longer the movie is playing for or the incoming emails. Sure other displays differ in the sense that they do offer more functionality due to the fact, that they act as actual secondary screens. These have the downside, that applications need to be assigned to that secondary output and that you are required to keep all of them running in the background.
So you need to ask yourself what you want from such a unit. Do you require complete usabilty just like a main screen - then the SDC Megtron is by no means the right choice. Do you value the fact that a single small application gives you access to a limited but important set of fact and information - then the Megtron is a good choice.