I try really hard to say, "Oh my gosh!" When I type "OMG!" I mean, "Oh My Gosh", not "Oh My God!" I think there are very appropriate times to use the phrase. To me, it's like calling out for God to hear a prayer. Sometimes if something is so emotionally painful I might say, "Oh my God", or "God help us" something like that. I do the same when I think something is so wonderful or beautiful it takes your breath away. I don't think it's cursing to use the phrase. I do think it can be inappropriate. It's almost meaningless when said over and over again, arbitrarily, and to me, God is not meaningless.
With that being said, when I was being baptized, I had to stand with my arms crossed in front of me. The minister came up behind me to dunk me in the water. He kind of kneed the back of my knee to let me know to lean backwards. I leaned backwards, looked in the pastor's eyes and said, "Oh My God!" His eyes opened real wide, and his mouth hung open!

To him, it must be a bad thing to say.
This is just my opinion. To each, their own.
