I brought one of these the other day, and to my delight it really did work the first time I plugged it in, no mucking around with settings or batteries.
The keyboard is very nice to use, with a lot of useful shortcut keys. My favourite thing about it is how the receiver clips onto the mouse, which makes it easy to carry around with you without losing it.
The only thing that caught me out was the size of the USB receiver, which I thought was one of those "always in" micro ones, when in fact it is about the same size of a mini USB key. But because of the way it clips on to the mouse, the size doesn't bother me.
Overall, it is a fantastic low cost wireless keyboard and mouse, and I would definitely get another one.