I've heard many believers (usually younger ones) use the expression "Oh My God" in conversation as well, and it always makes me cringe. One of the issues here is that we are called to be set apart from the world, and a refusal to treat God's name lightly is a great, practical way Heed that call. Many Christians will use "OMGosh" or "OMGoodness." I think this is a good expression that sets us apart as those who revere God but don't have our heads in the sand, while maintaining the holiness of God's name. I also think just finding a different expression to convey the same emotion may be the best option. What do you think? What do you say in those situations?