Macbook Air 2011/2012 battery and performance in OS X Mavericks

I think it's a bit early to tell. The older models surely will benefit, but some features such as Timer Coaslescing won't be available on older devices, because the processor must support this particular feature.

See for details: http://arstechnica.com/apple/2013/06/how-os-x-mavericks-works-its-power-saving-magic/

 

That's obvious nonsense. Timer coalescing, app nap, and compressed memory work on ALL computers which support OS X 10.9.

 

... and applications might need to be modified to use those features too.

If your App does not react to certain notifications, it will behave as it always did.