I've posted this to the issue tracker but I suspect that it might not be an "issue" but just something I'm missing, so just in case, let me ask here.
There is a LESS plug-in for PhpStorm that comes bundled. *.less files are indeed recognized, in that a little "LESS" icon appears next to the *.less files, but it appears that the "support" ends there. Code completion (with Ctrl-SPACE) does not work for me as it does for *.css files. I assume it's supposed to right? Is there some place in the Settings that I need to enable code completion for less files?
I'm using PhpStorm 2.1.4.
As I said, I posted this to the issue tracker so please vote it up if you also have this problem.
Also, I posted a question about it on StackOverflow with little luck so far.