I say semi-true in the sense that it's not wholly inaccurate. Valuable and thoughtful posts are rewarded and up-voted.
However, if my goal were to game the system for maximum karma per unit of time & post, I would contribute comments to hot-button issues that were in line with the prevailing mentality.
This is not to be facetious at all. I'm sure the moderators are well aware of this, but it's quite astounding how many up-votes are thrown around in discussions on polarizing topics (e.g. gender issues, NSA surveillance, etc.).
Often I see threads in new submissions which ask for quick feedback to a startup idea or blog post. They would never get upvotes enough to hit the front page normally, and so I would rarely get more than 1-2 upvotes for them.