It works fine with Snow Leopard, I've used it a long time with that OS.
However, since I skipped Lion and have upgraded directly from Snow Leopard (10.6) to Mountain Lion (10.8) I have lost a lot of the smooth flow and feel I got used to with my Wacom Intuos3 tablet and stylus. No matter how I set my options in either the Wacom preferences or the brush settings within Manga Studio EX 4, I can't seem to get rid of the lag that makes quickly-drawn circles come out with straight edges and lines appearing where I did not draw them, like the "correction" is set too high, but no matter if I turn it off or lower it, nothing seems to fix it and these are all the same settings I had before upgrading.
I could not find any discussions online about this, and wonder if I am the only one having the problem. Smith-Micro support only suggested unplugging the Wacom and re-installing the current driver, but that has not helped.