Open-source software often times as very poor support options. Forums and IRC are not substitutes to a dedicated phone support line that's manned 24/7.
That is simply wrong. A wide used and successfull OSS Software (CMake, Subversion, Apache, Vim, Eclipse) to name just a few of those we use in our Company (a very Big Company with more than 700K Employees) have excellent support. It comes in forms of Forums, thousand of Google hit's on every problem and of course IRC and Mailinglists.
As main user or tool responsible person of some of those applications, I never encountered a Problem that I couldn't find quality problem solving information for.
CSS support via closed ticket systems that aren't even indexed by search engines simply can't provide a similar support in my eyes.
Open Source Software comes along with "open problem solving" and that is a big advantage over their closed source counter parts.