A great game, but there are some concerns for parents.
I think this is a very fun and creative game. One thing that parents should know about it is that you can get an addictive drug called no-no powder and when you take it you feel great until you crash and then you have to take more or you die and go to hell. You always go to hell when you die (which happens when your energy gets too low) but you can come back to life. There is also a part of the game where you battle the Rook (an evil crow type creature) there is no violence but people can die and the Rook flys at the screen which may be frightening to young children.
I never got a chance to play this myself; so I don't know how good it was. However, Glitch has been shut down as of December 9, 2012 (according to Wikipedia). A fan project using the source code of Glitch (called 'Eleven', currently) is currently in the works, however. Maybe someday it will be open for beta testing.