Many here are posting what the various results might be if you win the hand and lose the insurance, or vise-versa, or win both, or lose both -- and use that to influence whether insurance might be a good thought.
Remember -- all of that is incidental! When you have any hand, be it 20 or 12, you'll always win or lose the hand itself just the same whether you took insurance or not. Nothing can change the outcome on your hand.
And if the count itself doesn't warrant insurance, you'll just lose money on all those combined insurance bets.
Hence, I believe in betting reasonably enough that you don't need to take insurance when insurance is a liability -- but only when you stand to turn a profit on the insurance bet (aside from cover plays), and let the hands take care of themselves, the way they will anyway.