Yeah, I don't see why is there such jubilation about this decision. I thought it has long been established that death threats aren't protected speech.
It is well settled that true threats are not protected speech. However, the constitutional issue in this case was about what the First Amendment requires the government to prove in order to deem someone's speech to be unprotected threats in order to convict them for making threats. The government here argued that it need only prove that a reasonable person would feel threatened by Mr. Elonis's facebook posts. The defense argued that the government must prove that it was Mr. Elonis's subjective
intent to threaten. That could potentially make a big difference in the age of social media where it's hard for a speaker to know what audience his facebook posts might reach and much easier for someone somewhere to take something the wrong way.
The court of course dodged this question by reading some (still unclear) mental state requirement into the statute as a matter of statutory interpretation so as not to have reach the constitutional question.