Apparently there IS A PROBLEM with these Microsoft nano transceivers. Just checkout the reviews on amazon. It seems that all the bad reviews stating problems with the transceiver started at the end of 2009. It explains why the price is so low too. VERY ALARMING! I wanted to get the nano transceiver so I could leave it attached all the time. Interesting there doesn't seem to be an issue with the Logitech's mouse small transcievers.
Amazon.com: Customer Reviews: Microsoft Wireless Mobile Mouse 6000