Pros: Like having a pair of tiny Albert Halls for each side of your head
Cons: You will spend a fortune trying to get a small improvement
These are simply the de facto best headphones at this price. They have a dark, slow sound that's suited to strings, guitar and vocals, and their matched drivers mean that centre-stage vocals will actually come from between your ears.
These don't so much break in, rather you get used to their reproduction. I can't recommend these enough, and everybody should spend some time with these, whether they take to them immediately or not.