I want to start by saying that while I have not owned it for very long, I have had absolutely no trouble with this keyboard. The only quirk is that to turn it off, I have to set it to a different frequency so that my tablet does not keep looking for it, but otherwise, very easy to use (and not the keyboard's fault). It connects immediately, and was recognized by my tablet very quickly. Setup took less than 2 minutes, and the packaging was nice as well as the carry-case (just a cloth cover, but still nice to have!). Overall, I think this is a fine, well engineered product.
Unfortunately, though, I am returning it for two reasons. The first is that it is a little too small for my tastes. A small grip I have with the design (not the operation) is that the right shift key is too small, leading to me often being unable to find/press it. Furthermore, I have to type fairly slowly to not mistype, though I was getting better, and probably would get used to it fairly quickly.
The second reason is that I bought it for use with my tablet, but I came to realize after some use, that I would not really be doing enough typing on it to warrant a $40 keyboard. I do not do much typing (aside from online on my laptop like right now) anyways, and the tablet is more for media consumption than actual work as I can do most things much more quickly on my laptop. I rarely used the keyboard and cannot find a use for it.
Overall, I find it to be a well engineered product and would give it 5 stars based on operation. However, for my own use, I cannot justify such an expensive keyboard when the on-screen keyboard for my tablet (acer iconia a500) is good enough for the occasional typing. I give it four stars for this reason as I cannot see the need for such a small keyboard, but others may differ in their opinions on this.
As a final side-note. It works well on applications that allow external input for controls (games)! Also, for an android tablet, the esc key works as a back button, but the windows key or win+d does not work as a home button! =(, and the media keys all work too.