Sin is a perfect example of a company running low on ideas and retreating back to the adrenaline rush of higher graphics quality and more blood. It's not boring but unfortunately Activision is expecting the public to catch up with faster machines and more processing power. Not everyone out there is fired up enough to spend the multiple hundreds of dollars to catch up. As a game, Sin is creative enough but it still is one dimensional. Most of them stick to alien encounters and such.
Sin is an urban based crime stopper with plenty of firepower to go around.
However, as with most 3D shooters the creators need to slow down your level descent so what better way then a required key to continue to the next level. After years of this sort of pattern key finding has just become annoying. Most gamers are well aware of the effort the developers take in coming up with their premises so key finding and button pushing have become tiresome long ago. Between this and graphic lag time most gamers won't care much for Sin. Those who are up to standard and like a decent FPS will probably like Sin but with so much competition out there in the market they won't be enthralled by any means.