I use the Logitech® Cordless Desktop® LX 300. The device works quite reliably from 15 feet away. I've only had a few hiccups with connectivity between the keyboard and the pc, but it was not due to the distance, it was due to the computer freezing a bit and not recognizing the keyboard...
The installation was quite simple - you just hold a red button down on each device for a few seconds. Thereafter, the keyboard is plug and play. No need to reinstall on reload, restart, etc.
I love it - I use it in conjunction with a wireless mouse from Logitech as well...
