I've noticed that many Russians use the name of God rather freely, as if it's no taboo at all (contrary to the English culture). If I understand correctly, "О Боже мой!" doesn't precisely translate to "Oh my God!": the former is perfectly acceptable, the latter is almost cursing.

Is that so? Is "using God's name in vain" considered disrespectful/rude/vulgar in any way similar to the way it is English?