I bought this because it was cordless, and suprisingly cheap. My first dissappointment was the fact that the mouse was not optical. Admittedly this was a big oversight on my part, not the fault of logitech.The keyboard: It seemed quite a good keyboard initially, with hot keys to load your favourite programs or websites, and looking rather nice. However, it is VERY sensitive to spills. I split a very small splash of water onto the keyboard and a number of the keys stopped working.
The mouse is very comfy, and has a nice quick switch button which acts a bit like Alt+Tab. However, it is very easily accidentally pressed due to its location. Also with it being non-optical it jerks a lot.
The wireless technology is good. The keyboard responded instantly and the mouse seemed OK apart from the inaccuracy caused by the ball.
So I wouldnt bother getting this kit, unless all you want it a very basic wireless desktop. After I had this I bought a logitech MX-700 mouse which is excellent, and a labtec internet keyboard, with the same hot keys as my logitech one. The keyboard was 7 pounds and the mosue was about 50.
Really... dont bother
A must buy to reduce cables - and a very nice keyboard too!
-As an optical mouse it some times has problems on certain surfaces that Ive not had problems with on other optical mice.
I already have one of these on my pc so when i saw this at such a goodprice i had to buy one for my Sons pc.
It performs exactly as specified and installation is easy, but there are a couple of things that would make me pick something else if I was choosing again. 1 - The weight of the batteries upsets the balance of the mouse. When you pick it up to reposition it on the mouse mat it tips backwards. I find.. 
The mouse is great. A bit smaller than I expected, but great if you always use a laptop... 
This mouse is ideal for most standard uses except for one thing - the batteries in the mouse weigh it down by a surprising amount. This leaves it heavy and clunky to operate.