Me, I see him as being not necessarily the ogre that the Irish perceive, but a flawed if occasionally brilliant man who fervently believed what he believed, and who made quite the mark on the world and in particular early attitudes in the North American colonies, planting the seed of our own Revolution over a century later.
If Cromwell indeed was prone to wide swings of emotion, and I do know that the poet Milton moved him not just to tears with his sonnet On The Late Massacre In Piedmont but to attempted retribution, then he had much in common with Jonathan Edwards.
For all the negativity, there are times when being manic-depressive actually is a favorable trait. Times of turmoil, primarily. You see it in a lot of prominent historic figures, particularly English royalty, oddly enough.
He burned people alive...pretty much a bastard.
Oh, please. Cromwell's disgusting career demonstrated that he only cared about himself. He revolted against his king for simply not having called upon Parliament (of which he was a member) but later, as dictator, he went so far as to actually dissolve a Parliament in session because it didn't give him what he wanted ("It's good to be the king" but 'it's better to be the dictator'). He killed his king for supposed treason against the kingdom while being, himself, the leader of the revolution which initially deposed him. He came to power championing the 'Levelers' and rallying them to his cause, but later, much like Hitler did the SA, he eliminated them after they had served his purpose. He established a psuedo-republic for the declared purpose of instituting rule-of-law, but then proceeded to run the country like a modern third world generalissimo. He destroyed the ancient vestiges of English monarchy in an attempt to end forever the inherited title but, in the fashion of the North Korean Kims, he established his son as his successor. Finally, he killed MANY people, all in the name of Christ, and all of them where Christian.
Cromwell was, truly, the PERFECT Puritan.