Tom's confirms the issue:
http://www.tomshardware.com/reviews/...l,2943-13.html

Several weeks ago, Michael Larabel of Phoronix reported that Ubuntu 11.04 suffers serious battery life regressions from previous versions of the distribution. His findings were originally specific to the kernel, and he received a lot of feedback on Slashdot and other forums asking whether or not this would manifest in real-world usage.


We not only confirm his findings, but also demonstrate that this issue has very significant implications in actual use. It also appears that the Unity interface is not the root cause. In fact, Ubuntu 11.04 with Unity gets more than 20 minutes additional battery life than Ubuntu 11.04 Classic. The previous release, Ubuntu 10.10 Maverick Meerkat gets over two hours more battery life than Natty Narwhal, regardless of the user interface. This was probably the main deciding factor for Asus when it recently chose to ship Ubuntu 10.10 Maverick Meerkat as opposed to 11.04 Natty Narwhal on the new Eee netbooks


Mobile users are urged to seriously consider these results, and possibly even avoid the Natty Narwhal. On the other hand, Lucid has serious issues with hibernation, as does Maverick, making this a difficult choice for road warriors. I hate to say it, especially in an Ubuntu review, but the mobile edge goes to Windows for now.