Following numerous reports online and in the support forums, Nokia have released a statement regarding the battery life on a number of Lumia 800 handsets. Two updates are due to address the issues, in early December and early January. Both which will be delivered through the Zune update mechanism. The statement reads:

We understand that some people have expressed concerns about battery life on the Nokia Lumia 800.  Early investigations show that the majority of people are enjoying the full Nokia Lumia experience without any problems.  A software update in early December will include improvements to power efficiency, while a second update in early January introduces further enhancements to battery life and battery charging.  Both are planned updates and will be made available via Zune.  We recommend that anyone who still has concerns contact local Nokia care representatives at their earliest convenience.

More details are on the Nokia Discussions Forum.