The handset is available exclusively from T-Mobile and is loaded with stock Android 2.3 out of the box. Google employees have tried to come up with an upgrade and are on their second attempt. A recent update to Android 2.3.2 did not include a solution to the problem. Of course, Google will not let this problem last forever, and eventually an upgrade will be sent. But for now, Nexus S users have to keep their fingers crossed when on an important call to try to keep away the evil spirits that are causing the phone to reboot in the middle of a call.