Well, this puzzle was claimed to be "the toughest" several years ago ; things have changed now and there are lots of harder puzzles available. Anyway, finding a logical way to solve this one is a real challenge. Using guesswork, french player Yannick Meyapin solved it in 15/20 minutes during a competition.

Here is a puzzle which is theoretically even more challenging, with or without guesses :

. . . | . . . | . 3 9
. . . | . . 1 | . . 5
. . 3 | . 5 . | 8 . .
------+-------+------
. . 8 | . 9 . | . . 6
. 7 . | . . 2 | . . .
1 . . | 4 . . | . . .
------+-------+------
. . 9 | . 8 . | . 5 .
. 2 . | . . . | 6 . .
4 . . | 7 . . | . . .

(Golden Nugget, one of tarek's puzzles)

Well......I am not a very good sudoku solver....but dnt know how i solved this sudoku in around 13 minutes....used couple of guesses and it worked for me...LOL