Engadget hosted a couple of Windows 7 demonstration videos. Microsoft promises a lot of things such as faster boot ups, better power management, better memory management and more. The new OS will even be able to use your video card to offload the system memory:
In addition to an overall reduction in the number of services launched at startup, faster booting is achieved by loading device drivers in parallel instead of sequentially. Windows 7 also manages wireless radios better allowing them to drop below 100% power draw while managing the connection. And by tweaking the OS kernel, the CPU can sometimes run at a lower frequency and stay idle longer. This results are a minimum of 11% better battery life for Windows 7 compared to Vista -- and we're still only talking about pre-Beta Windows 7 software, mind you. Nice. Windows 7 also promises better memory management. So instead of managing all the background windows, Win7 offloads this to the GPU, for example -- system memory is then free for your applications and data.