The one and only new twist is the plot gimmick: a grovelling apologia to Pauline Kael and her proxies, who accused the original of pandering to vigilantism and labelled it fascist. In bending over backwards to disprove that charge the film comes off as cynical and, far worse, disrespectful of the audiences who loved the original just the way it was. ("I'm afraid you've misjudged me," Harry says at one point.)
Apart from that one dubious innovation it sticks like super-glue to the established template: the rookie partner, the battles with superiors, the snarled catchphrases, the selection of incidental assignments (including one that Harry happens to intercept while eating at a hamburger restaurant and embarks upon still chewing)... all are present and correct. It's also far too casually paced, a ninety minute movie that comes in at a flabby 124; with tighter direction and editing at least half an hour could have been trimmed without removing any one scene in its entirety.
And yet, despite all that, the bastard works, and never even begins to seriously tax the patience of anyone who loves to see Clint going about this kind of business. Just having him show up in the role is to have half the film's job done: it would have to be terrible to fail with that kind of a head start, and for all its faults, it's far from that.