I picked up a Microsoft Wedge Bluetooth (Surface edition) and am having the same problems as you all listed here. Boot SP, turn on Bluetooth mouse, works fine for about five minutes and then the mouse starts to get super laggy (this lasts for a few seconds) and then the mouse stops responding and the Wifi is dead. I have nothing plugged into the USB port and no other Bluetooth devices connected. Running Windows 8.1 on SP 128gb model. Reboot and I'm back working for a few minutes again.
Unusable and I purchased the Bluetooth mouse so that I could have my USB port free when I need it.
MS - this has been going on for quite some time from the looks of this thread - this is basic functionality that must be fixed!
-Larry