How much RAM do you have? OS X is quite memory hungry and is terrible when it has to page. I'd recommend maxing out the RAM if you haven't already. I'm guessing you have a regular hard drive too. An SSD will make it feel like a new machine.
Also, Mavericks is much snappier than ML from what I've seen so far and makes much better use of RAM.
Also, Mavericks is much snappier than ML from what I've seen so far and makes much better use of RAM.