I'm seeing around 1 to 1.5 more hours of operation on Mavericks on a 2012 Macbook Air 11". Now, that is not for web browsing but for development & debugging with Xcode, so I'm usually never reaching these marvellous 6+ hour rates, but with Mavericks it went basically from 3-4 hours to 4-6 hours, which is fantastic.
I'm pretty sure that that will only widen the gap between OSX and Windows on Laptop hardware.
The 13" Macbook Air could then theoretically reach 17 hours of operation time!
There are probably no benchmarks yet, but from my experience (I use both 10.8 and 10.9 regularly) Mavericks does a better job on battery than Mountain Lion, with about 1 hour of usage added. This is on 2012, 13" Air. The 2013 model will probably see even better gains.
Strangely enough, my Windows 8.1 managed to suspend everything yesterday. Not only the Metro apps that I didn't use, but also Explorer and every other desktop application I used. Wonder how that happened (although I used to suspend applications manually before if I wanted to pause them somehow, e.g. CPU- or I/O-intense long-running things).
I cannot undo a crash, but I can resume applications just fine. In that particular case I tried hibernate first which led nowhere, so essentially yes, it was akin to a crash. Still puzzling, as that never happened to me (and Windows versions prior to 8 didn't use the suspend/resume functionality anyway).
I have a 2010 MacBook Pro and it's about 10-20% better battery life.
Mavericks IMHO is designed for the newer MacBooks which really need to get to 8+ hours battery life for it to change people's behaviour i.e. being able to realistically leave the power adapter at home.
Also there are some decent performance improvements that would mean less cpu usage (or bursts of them, which is more power efficient).
Are there any benchmarks? Or is it still behind NDA?