I just put a 7260 in a Sony 15" S Series. Previously it had a 6235. I also had issues with the bluetooth. With the generic windows driver the mouse disconnected after a short time. It would reconnect if I turned it off and back on but only for a short time. I found the 3.0.1304 BT drivers and installed. The installer output that it was removing 2.6 drivers (from the 6235) and installing the 3.0. After the install I had the same issue.
I noticed in windows 'Administrative Events' in event viewer I seemed to be getting HidBth events: "Bluetooth HID device either went out of range or became unresponsive." when the mouse became disconnected.
Solution: I disabled Power Management for the device and my mouse has been connected for hours. Hope that helps someone. Hopefully working drivers are out soon.
Power Management: Device Manager -> Bluetooth -> Intel ... Bluetooth ... -> (right click -> properties) -> "Power Management" tab -> Uncheck "Allow this computer ... to save power"