Even though they disagree, they're still on good terms.
Literal
They [topic-は] opinions [object-を] differ [despite-のに], as-always close [subject-が] good.
意見を異にする means 'to have different opinions.' ~のに marks the concession: 'despite disagreeing.' 相変わらず means 'as always, still.' 仲が良い means 'to be on good terms.'