I'm quite partial to the occasional puzzle but I wouldn't say I'm any good. I tend to do puzzles from the site
http://www.websudoku.com and select any one of the four categories (Easy, Medium, Hard, Evil) depending upon how much time I've got. My average time on an "evil" puzzle is a little over 40 minutes.
I stumbled across a rather good sudoku solver a couple of days ago,
http://www.sudokuwiki.org/sudoku.htm, which shows how it solves puzzles by eliminating the various numbers that are impossible, one step at a time. I found it very interesting that the solver employs up to 20 different strategies to eliminate numbers. I tried a few of the "evil' puzzles from websudoku.com and watched the solver at work. To solve an evil puzzle, it hardly ever has to use more than about the simplest 4 of the strategies available to it. I would imagine that this illustrates how much better at this kind of puzzle computers are than are humans.
I tried a "diabolical" puzzle from the solver's own stock and it was very interesting as such weird devices as "XY-wing" and "Simple colouring" were employed. Even though the logic was, apparently, laid out before me, it wasn't easy to see exactly what was going on.
Does anyone else have a dabble?