A lot of web servers that host websites do run on Unix and Linux, so the threat is very real. The threat itself is rated a 10 out of 10 by the CVE as well. The exploit is easy to run on a computer which is of concern. Remember the Heartbleed bug some months back? This is on par to that vulnerability. The next worry is that if, or more likely when a worm is created, it can replicate and compromise thousands or maybe millions at a fast rate.
For those that have Apple computers, Apple has mentioned that for someone to get control over your computer using the vulnerability is very hard to do and Apple users shouldn't worry. I do agree with this assessment as well. In addition, Apple has released a patch on Lion, Mountain Lion, and Mavericks that you can download and install on your Apple computer.
Overall, we all should be concerned about Shellshock as the computers that are being infected with this easy to run and use exploit by the attackers are computers that hold credentials, personal information, anything you can think of really. Just stay vigilant and make sure to watch any news on Shellshock, and hopefully it doesn't effect a company that holds your personal data or a website that you go to on a daily basis that could infect your computer. Aloha!