French Blogeee.net ran several battery benchmarks which showed painfull results, especially when the 4400mAh battery is used. Many Eee PC 900s are shipped with these underrated batteries (because of shortages) instead of the 5800mAh batteries which are standard.

After just 1 1/2 hour of web browsing & document editing with the screen brightness turned all the way up the battery was empty. With a standard Eee PC 701 5200mAh battery things did got a little better.