Well it depends what sort of tactics you employ; If your site has content scraped from other sites, popup adverts or generally poor quality content, giving the user a poor experience, then yes you should be worried.
The Panda update has been one of the most talked about updates from Google since its launch early in 2011, but all Google is trying to do is return the best results possible for any given search by displaying the most relevant results and content for the user.
Panda 4.0 again is another algorithmic refinement to stop sites with poor quality content from working their way to the top of Google's search results. Since the start of this update in 2011, Google has been refining this algorithm to produce the best results possible. As in all other aspects of life, there are people who want to try and cheat the system for a quick win and Google is trying to cut out those sites. Most successful businesses are built up over time, with hard work and focus. Getting long term sustained rankings should be no different, you get out what you put in. Write your own content, write it to enhance the user experience, not to try and trick Google into ranking your site higher by stuffing your copy with keywords, pop-ups and adverts.
Let's face it, if you create great content, that content will be shared across many platforms, increasing your sites authority and in turn your sites rankings, so why would you try to take a short cut?
Googles Panda updates are designed to penalise sites with a poor user experience, and enhance the rankings of sites with a positive user experience. If Google didn't do this, their search results would be full of poor quality spammy sites and users would simply use another search engine.
So when you are adding content to your site imagine yourself reading it. Does it tell you what you want? Is it engaging enough for you to continue reading it? Is it good enough quality for you to want to show it to your friends? If the answer to all of those questions is yes then you probably will have added some great content to your website.