(I'm using OSX)
I tried tried to autocompile .less files by using less.app (http://incident57.com/less/). You can set a watch on a specific folder and when you save a .less file the app autocompiles it to a css file.
When editing a .less file by using textmate this works like a charm anytime I save the file less.app compiles it, but when I try to do this in phpstorm the file never gets compiled. It seems the less.app doesn't recognize when phpstorm changes a file. Is this a bug?