The last dungeon I designed had probably 6 or 7 puzzles in it. Some weren't obviously puzzles but others were. I used a sudoku like puzzle (where a successful skill roll gave them clues), a rotating pillar puzzle, and a floor tile pattern puzzle. We all had a lot of fun, especially when the traps were scaled on how bad each attempt was missed. Some of the puzzles took slightly longer than 10 mins to solve but just about everyone was involved. One puzzle was very difficult, it was an iron door with multiple locks (levers and pulleys) and traps, and it was a fake, but at the same time there was a constant trickle of orcs, the characters were very pressed for time. They were only 2nd and 3rd level.
I think the best puzzles involve a little foreshadowing in the game that seem difficult but can be somewhat easy.
Bruce