We all know what that means when we see it. You can say it means "Oh my goodness," or you can say something stupid like, "Oh, actually I just mean 'Oreos mean greatness!'" but we know what it really means.
I don't like that phrase, yet I hear Christians using it. I can tolerate a certain amount of bawdy language, depending on who is using it; I realize that not everyone objects to it. However, two things that make me see red is use of the F-bomb, and when people use God or Jesus or Christ as some kind of profanity. I don't care to exercise my freedom in Christ to employ such terms. I consider that a rather hollow benefit of being "free" in Christ.
D.A. Carson, in the book The God Who Is There, discusses the the Ten Commandments. He goes through each one briefly. At number 3, he discusses "God's Importance." He makes a great observation about using the name of God in a careless way:
The reason we are not to say "Oh, God!" when we hit our thumb with a hammer or say "Jesus!" when we are disappointed is precisely because it diminishes God. If you were to be so bold as to turn to a person who has use Jesus' name because he has hit his thumb with a hammer and say, "I wish you wouldn't use my Savior's name like that," he would probably reply, "I do not mean anything by it." But that is the point: he does not mean anything by it. That is precisely why the usage is "profane," that is, common. Using the name of God or Jesus when you "mean nothing" by it is not profane because you have spoken a magic word that you are really not allowed to use, as if only priests can say the right abracadabra. The usage is profane beause it is common, cheap. We are dealing with God, and we must say and do nothing that diminishes him or cheapens him. It is at best disrespectful, ungrateful, and demeaning; at worst, it de-gods him and thus sinks again in the level of idolatry.