I would say the answer is yes and no. I think you need to parse it into several different questions.
Has this been done before? — Yes.
Yes, on numerous occasions the President has extended "Executive Amnesty". Here are a sampling (not at all inclusive) of such actions:
So should we all just chill out? — That's not answerable.
What about the part, as you so elegantly and colloquially stated:
"(so we should all just chill out?)"
Due to the numerous precedents, calling for actions such as impeachment or a government shut down are partisan bickering and not at all called for. Sadly, we don't have any way to measure if we really should be chill, or concerned. The main considerations and issues as I have been able to gather from the talking heads are:
- Will the newly minted legal status cause a burden on the welfare system?
- Will newly minted tax payers help the US tax base?
- Will this alleviate stresses and demands on the immigration courts and other services involved with processing immigrants?
- Will this keep families together?
- Does the scope of this make it somehow intrinsically different?
At this point, we have no way of specifically answering these questions.
Is this exactly the same as previous times? — No.
As to the "no" portion of the answer, I think the main difference is simply a matter of scale at this point: the Pew Hispanic Center estimated in March 2006 the number of illegal migrants in the US to range between 11.5 and 12 million, all of whom may not be concerned by this executive order (the number being tossed about in various media outlets is 5 million). This action has the potential to affect more people than any other executive amnesty that I am aware of.