At the time of this writing, the Zagg has them on sale for $39.99 from the regular $80.
So what makes it so great? Answer: portability and flexibility.
I have a few iPad keyboards and they work great for the most part. Except, they tend to get bulky and negate the advantage of having a tablet. Next, when you get a different tablet, the keyboards are often form-fitting for a specific generation of devices. You end up buying a different one when you get a new tablet. Importantly, the bulk wears you down. You may not need a keyboard/case combo all the time. When you are watching Netflix, you definitely don't need a keyboard. Hence, many of keyboards tend to fall into my desk drawer.
The Zagg Flex keyboard is compact and there is a simple cover that is used as a kickstand. The kickstand can even carry the weight of some covers. I don't have to remove the existing cover to use the kickstand. As you can see below, it is smaller than even the Apple Bluetooth keyboard.
Now, I just leave the keyboard in my bag and use it whenever I want.
Like most tablet keyboards, this one uses micro USB for charging. There is a toggle for iOS/Android. I assume this is for the key mappings for certain functions like home and menu.
Overall, this is very flexible. I can easily use my 7" Galaxy tablet or various smart phones. Overall, I am happy with this purchase.