It's lazy and boring and not fun at all. Simon is not a fun toy, not for more than five minutes, after which it is a nuisance.
There is no reward. Either you have fast enough reflexes or enough patience for unnecessary repetition.
These are barely tolerable in God of War, and even then there's no reason to use them more than once or twice, not all through the games.
They absolutely ruined Fahrenheit. Here's a sequence made of twelve different timed button presses, if you miss one you die and have to start all the way at the beginning, have fun. Not much of a loss, because the game itself was shit.
They may as well put electrodes on controllers and administer electrical shocks every time you miss one of those button presses. At least it would get my adrenaline going.
My most recent encounter was in the Jericho demo, an okay shooter capped by a Pres Butan sequence that added nothing to game except a chance to reload and try it again. Easy enough, but pointless.
The grandfather of these sequences is the Dragon's Lair laserdisc game. This game was not fun. It was cool to watch if you had a friend with perfect recall to play through the whole thing, but it did not provide enjoyment in a traditional sense.
Stop doing this, designers. You do not want to rely on either of these two variables to keep people interested in your game: Reaction time or Patience.