Charlie Savage has the entire text of the FBI's Miranda memo, and there's not much to see here:
As noted above, if there is time to consult with FBI-HQ (including OGC) and Department of Justice attorneys regarding the interrogation strategy to be followed prior to reading the defendant his Miranda rights, the field office should endeavor to do so. Nevertheless, the agents on the scene who are interacting with the arrestee are in the best position to assess what questions are necessary to secure their safety and the safety of the public, and how long the post-arrest interview can practically be delayed while interrogation strategy is being discussed.
Nevertheless, the fruits of that questioning aren't admissible in court:
The Supreme Court has strongly suggested that an arrestee's Fifth Amendment right against self-incrimination is not violated at the time a statement is taken without Miranda warnings, but instead may be violated only if and when the government introduces an unwarned statement in a criminal proceeding against the defendant.
Right. The administration has tied themselves in knots by arguing that Miranda isn't an obstacle to interrogation and then giving agents explicit permission to delay Miranda if they want, but the memo basically gives agents permission to do what they would probably already do under the circumstances. It does not allow them to admit those statements in court. This doesn't really change much about how Miranda works; my worry is that it mostly confirms Republicans' arguments rather than making them feel better about the whole thing, since Miranda is really a non-issue anyway. Republicans didn't mention the issue at all until a Democrat was in office.
Still, let no one say this administration is not all sensitive to criticism from the left. The only reason I can see for leaking the memo in its entirety is assuring people that the administration hasn't sanctioned an end-run around the Fifth Amendment.