Nokia on their official support discussion forum have stated that the recent update v(1600.2483.8106.11500) that was released for Nokia Lumia 800 has indeed fixed the issue of battery problem of the first Nokia Windows Phone.
Nokia after receiving a lot of complaints from the users of Nokia Lumia 800 worked on to improve the battery life and enhance standby time. But even after the update the battery issue was not fixed according to some of the customers. In reply to that Nokia suggest that they should not use a diagnostic tool which can be opened by a code ##634#. It actually is designed for internal testing purposes. More accurate information about battery is available with battery saver option which can be found in Settings>Systems>Battery Saver.
Also they have stated to use only the original Nokia Fast USB Charger AC-16 only. In relation with Camera and Audio issues, Nokia only stated that it will soon be fixed with another update that will be released, though no dates were mentioned. So we hope that the battery issue is indeed fixed and those who own Nokia Lumia 800 gets the advantage of the update.