I was using Mountain Lion, and if I open 'About this Mac' menu, "Graphics" value was "Intel HD Graphics 4000, 512 MB". But... Today I've installed Mavericks on my MacBook Air 2012, and i noticed strange thing. It's not 512 MB now - it's 1024 MB.
Mavericks made graphics improvements so it doesn't use a lot of vram now?
Also games such as 'Minecraft', 'Black Ops' are working without fps drops, stable at 50-60 fps. ( @Mountain Lion it was 30-40, fps drops ).
Or it is just me? ;D