I have the MS Bluetooth set. For the most part I like them. I like the keyboard and the shape of the mouste, but have a few problems with them.
My first one would be that they go into hibernation too quickly in my opinion, and therefore you get lag when waking it up. If you're playing games it doesn't do it because you're constantly pushing a button, but for browsing it seems like by the end of reading something it has to wake up.
The other problem I've had is that they seem to disconnect. I'd have to go into the bluetooth setup and have one of them setup again. It takes about 20 seconds, which isn't bad, but can be a pain sometimes. Most likely what happens is I hit the connect button on the bottom of the keyboard causing it to do this, so most likely its me thats the problem. Its pretty much always my keyboard that does this.
Other than that (and the blue coloring which doesn't go with my red, black, and gray theme) they are nice. I like the shape of the mouse and it has nice rubber grips on the sides. Nice clicky scroll buttion and the side buttons are good.
My recommendation: get the Logitech Neovo if you can (its about $200), if not then either the lower end Logitech or the MS set would be good.