The bigger problem wasn't really the actual plugin breaking websites, but the huge lack of support in the forum. Only in the last few days iThemes support account showed up to answer some threads, leaving others untouched.

Yes, it is a free plugin and people use it at their own risk and support isn't guaranteed - but there's a certain ethical responsibility to users of your plugin that carries your company's name and has a commercial support to help resolve issues you created with a new version. Even if you overlook the ethics, look at the PR storm this has caused.