Poker math is definately useful for those extremely close decisions. However, I think you only need an intuitive understanding of the math in poker. Hand randing skills are far more important, and the better you are at hand reading, the easier your decisions become. In other words, you will, by your intuitive understanding of poker math, make the best decision. Without being able to place an accurate range on your opponent, your math will be off, while if your range is accurate at first, your "flawed" math will only have a little bit of error.