Wikipedia: Augustus: "In the beginning of his Annals, the Roman historian Tacitus (c. 56–c.117) wrote that Augustus had cunningly subverted Republican Rome into a position of slavery. He continued to say that, with Augustus' death and swearing of loyalty to Tiberius, the people of Rome simply traded one slaveholder for another. Tacitus, however, records two contradictory but common views of Augustus...
...Intelligent people praised or criticized him in varying ways. One opinion was as follows. Filial duty and a national emergency, in which there was no place for law-abiding conduct, had driven him to civil war—and this can neither be initiated nor maintained by decent methods. He had made many concessions to Anthony and to Lepidus for the sake of vengeance on his father's murderers. When Lepidus grew old and lazy, and Anthony's self-indulgence got the better of him, the only possible cure for the distracted country had been government by one man. However, Augustus had put the state in order not by making himself king or dictator, but by creating the Principate. The Empire's frontiers were on the ocean, or distant rivers. Armies, provinces, fleets, the whole system was interrelated. Roman citizens were protected by the law. Provincials were decently treated. Rome itself had been lavishly beautified. Force had been sparingly used—merely to preserve peace for the majority.
According to the second opposing opinion:
filial duty and national crisis had been merely pretexts. In actual fact, the motive of Octavian, the future Augustus, was lust for power ... There had certainly been peace, but it was a blood-stained peace of disasters and assassinations.
In a 2006 biography on Augustus, Anthony Everitt asserts that through the centuries, judgments on Augustus' reign have oscillated between these two extremes but stresses that:
Opposites do not have to be mutually exclusive, and we are not obliged to choose one or the other. The story of his career shows that Augustus was indeed ruthless, cruel, and ambitious for himself. This was only in part a personal trait, for upper-class Romans were educated to compete with one another and to excel. However, he combined an overriding concern for his personal interests with a deep-seated patriotism, based on a nostalgia of Rome's antique virtues. In his capacity as princeps, selfishness and selflessness coexisted in his mind. While fighting for dominance, he paid little attention to legality or to the normal civilities of political life. He was devious, untrustworthy, and bloodthirsty. But once he had established his authority, he governed efficiently and justly, generally allowed freedom of speech, and promoted the rule of law. He was immensely hardworking and tried as hard as any democratic parliamentarian to treat his senatorial colleagues with respect and sensitivity. He suffered from no delusions of grandeur.
Tacitus was of the belief that Nerva (r. 96–98) successfully "mingled two formerly alien ideas, principate and liberty"...