The short answer: like a moderate headache; it hasn't been nearly as bad as, say, a sprained ankle or wrist. Having my braces restrung was more painful than the surgery. Now for the long answer. My surgeon started with two shots, neither of which bothered me. (Full disclosure: I have a high threshold of pain and no aversion to needles. The surgeon remarked that most people find the second shot painful.) For the next 45 minutes or so, I sat there with my mouth open while he worked on me, feeling nothing. I saw him using a socket wrench on me (I've turned enough of them to know one), then saw him pulling thread. Finally, he showed me an x-ray of the titanium screw in my upper jaw. He explained that he didn't like the original position of my eye tooth, so he put the screw where there was more bone. Extracting a tooth and putting in an implant in one sitting was pushing the envelope, as he put it, but in the worst case, he'd extract it, let my mouth heal, and try again
Do-it-yourself health. Low-carb, mostly evolutionary.