According to Engadget, even in a Pre-Beta state, Win 7 is making great progress

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. 

Nice, indeed 🙂