Gears is an awesome action game and you will enjoy every single moment of it.
Now to the sound, let me say that the sound in Gears is very well made, the music fits every situation perfectly and it's very well composed, the voice acting is also excellent (especially Cole's voice hehe) and the gun fire sounds is very realistic. Last but not least, comes the gameplay, wich is awesome, the cover system works very well and makes Gears diferent and more strategic than others run-and-shoot games, oh and you're gonna love using the chainsaw. The single-player will take you about 5 to 8 hours to complete, but then there's still Hardcore and Insane mode to do, and after all that you have the multiplayer wich is great, the only thing bad is the glitchers, but you will love the feeling when you kill a glitcher.
Overall, Gears is an awesome game that should be played by all 360 owners that are mature enough.