I bought this to work alongside my Logitech S 510 Cordless Desktop and I wasn't disappointed. However, I find the mouse is a bit on the small side. I prefer a "taller" mouse so my hand cups over it and stops my fingers over-reaching the buttons. So I swapped the mouse for a "Cordless Click Plus!" which I had been using with the Logitech keyboard this was replacing. Much better. The only problem occurs when both mice are being used at the same time as the signals tend to interfere and slow down the pointer movement. But that's usually only when my girlfriend is using the other PC at the same time, so not too often (and bear in mind they are literally side by side).
There's a good range of customisable buttons pre-set (which can be set to other functions) and 4 "spares". A dedicated "Calculator" key is a nice touch and actually encourages me to use the Windows calculator instead of always reaching for the real thing.
Media keys: Play/Pause; Skip Fwd/Back; Volume Up/Down; Mute; Enlarge; Reduce and 100% image size. I like Logitech's larger Delete key. There's also a "Sleep" key to tell the PC to sleep, restart, log off or shutdown, depending on your choice.