Well, every OS X update so far has reduced in size. Mavericks is larger than the previous two, but it's also changed how it does swap and sleep images. I have 16GB, and /var/vm/sleepimage is only 8GB. I used it only hours ago, so I know it's been used in Mavericks.
Likewise, it only allocates a safe amount of swap based on what it thinks the current apps might use in a worst case scenario. That has been in for several versions, though. I have yet to use swap, and the two swap files are 64MB and 1GB.
Ah, interesting. So does it pre-allocate swap then? I use iStat Menus and since u/g to Mavericks it hasn't reported more than 1GB of swap used despite me having used it heavily (e.g. Aperture). under ML it regularly reported anything up to 8GB.
BTW, the pre-Mavericks amount of free space included the reported swap usage as shown by iStat.