Mueller is, of course, the right man for the job. He's smart and experienced, and he's not going to be bullied or influenced by the President or the White House.
Considering Rosenstein's reputation for fairness and integrity, it's not a surprise he decided to appoint a special counsel. What is surprising and very impressive is who he appointed and the way he did it.
He didn't ask the White House for approval; he just pulled the trigger and told the administration it had to deal with it. He gave the White House no time to try to convince him not to do it, and no chance to fire him before he did. Well played, sir.
As special counsel, Mueller has jurisdiction that is, at least on paper, very broad. He has the authority to investigate "any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump" as well as "any matters that arose or may arise directly from the investigation."
He can also "investigate and prosecute federal crimes committed in the course of, and with intent to interfere with" his own investigation. Things such as "perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses" are all within his jurisdiction. In other words, he can look into almost any issue relating to "the Russia thing."
It's important to note that, while Mueller is in charge of the day-to-day affairs of the investigation, he is not completely independent. He is subject to oversight by the deputy attorney general, and he can be fired for many different reasons, including "misconduct, dereliction of duty, incapacity, conflict of interest" and "for other good cause," an uncomfortably broad and entirely subjective reason that's easy to use as an excuse.
But I don't think Rosenstein or anyone else will try to fire Mueller.
I can imagine that Trump must now be thinking what a foolish blunder it was to fire FBI Director James Comey in the first place. Trump's passive-aggressive removal of Comey (reportedly via a note from his bodyguard while Comey was thousands of miles away) may well have come back to hit him in the mouth. Mueller is like Comey, but on steroids. He will have more power, more resources and the ability to focus like a laser on one investigation instead of having to run the entire FBI. He is indeed a "special" counsel.
If Trump or anyone else in his campaign is guilty of a crime, the appointment of Mueller as special counsel is really bad news for them. For the rest of America, it's a sign of hope.