AnandTech has written a 19-pages preview of Windows 7 RC, you can check it out over here. The article takes a look at the new features, performance, power consumption, battery life and more. Here's a snip from the conclusion:
Briefly, Microsoft has mentioned that they expect Windows 7 to be more power efficient on laptops than Vista, but so far this hasn't been something we've been able to corroborate. We suspect that better drivers will be necessary to extract any power efficiency gains out of Windows 7, so this is something that will require revisiting once Windows 7 ships.
Compared to previous first-edition release candidates such as Vista RC1 and XP RC1, Windows 7 is in a class of its own. While XP's RC1 was okay and Vista's was problematic, as best as we can tell Windows 7 RC1 actually lives up to the name of "release candidate." We haven't found any immediate bugs and the performance is great. If Microsoft were to resolve our hardware compatibility issues, they could probably get Windows 7 out the door right now with most people none-the-wiser that it's the same build Microsoft is calling the first release candidate.