Well, I highly doubt that Sigma would have a case to stand on. Judges look at if your content was factual. If you have evidence to back your case, you're quite entitled to state it. If a manufacturer doesn't like it, tough luck. When manufacturers try and sue for things like this, it makes a mockery of the legal system, since the legal system is NOT equal. Those with more money (i.e. the rich and powerful) are automatically given preferential treatment by the legal process. Many people choose to settle, rather than risk paying for expensive legal support. Supporting yourself legally is risky, and in some jurisdictions, judges heavily frown upon it. I find manufacturers who take legal action against people who speak their mind nothing more than bullyism taken to extremes. A point in example of this:
http://thomashawk.com/2009/02/canon-...fall-blog.html
And the best thing, Canon *lost*. Hooray for the little man.
Dave