Everyone knows that software has bugs and limitations and if we only have glowing comments about Linux, we aren't being honest. If you haven't actually used the proposed solution, say so. If you are available for making presentations about Linux, register with the Linux Speakers Bureau . Offer to help someone start using Linux. Follow up to make sure that they are able to use their system effectively.
Some people still believe that Linux and similar systems operate only in text-mode.
Make sure that they are aware of the availability of graphical applications, such as the Gimp . Seek out the tough questions, you may be the only one to respond and you may learn something in the process. However, if you aren't confident that you can respond with the correct answer, find someone that can. Seek out small software development firms and offer to make a presentation about Linux. If the opportunity arises, make a presentation to your employer's Information Technology group.