I've got Belkin's extended-range USB Bluetooth adapter at home. I use it primarily for Salling Clicker with my phone (controlling the iTunes that's in one room playing on a stereo in another room with speakers covering the whole house). Unlike with the D-Link adapter, I can get the "what's playing" info via Clicker from almost anywhere in the house, which goes up to about 20-30 feet from the adapter, with several walls in between. (The biggest problem spots are where I can stand with the furnace in between me and the computer... often get no connection there.)
The catch, though, is that while the BT adapter on the computer has a more powerful radio transmitter, the phone is still only a Bluetooth Class 2 transmitter -- so there's a fringe to the range in which the phone can receive info just fine, but trying to send commands back to the computer typically causes the phone to give up on the Bluetooth connection. So, it may or may not be much good for use with a keyboard/mouse, depending on just how much distance you're planning on trying to cover, and what obstacles to radio transmission might be in between.