Power usage in a typical laptop is roughly evenly split between hard drive, CPU, monitor and wifi
By 2009, most new laptops will use solid state drives This will reduce power usage by up to ten times from what the hard drive would have used. A 20% reduction in overall power usage.
There are bigger impacts from faster boot and restart times Plus database and application performance is better from applications that would have had a lot of paging from the hard drive.
A totally remade laptop and handheld devices with lower power usage would need a new monitor such as OLED version, and redesigned CPUs and wifi components.
OLED and advanced LED can get to 30 lumens/watt or about double the current standard, but very advanced versions can reach 200 lumens/watt or better
Cameras can be made 50-100 times more efficient