Sparingly. I have seen far too many people go BLITZKRIIIIIIIIIEG and think they'll walk away from it. Sure, you may have more HP, sure, you may have Hammerslam, but honestly, can't people work out that he's short range? You have to wait for them to come to you, and then from there on, you have to play it well. Stun them, slam them, and hopefully either finish them or have an ally around/general's minions around to facepwn the rest of his HP in the ground.
Or at least Blitzkrieg WELL. Why can't people learn this simple rule?