Hmm, I agree in places, and disagree in others. I agree on the practice of an upward slash or stab movement as your opening attack from the draw, as it leaves you in a more favorable position should the attack miss or be deflected, and it is more difficult to deflect and manipulate a low upwards slash or stab than it is a downward attack. Also, biologically speaking, the 'good bits' of your opponent are more vulnerable to attack from below. Groin, stomach, diaphragm, armpits, and throat are all fully exposed from below. Also, you have a better chance of clearing any interfering clothing on your opponent, such as a jacket.
Where I like to differ is one what the opening attack should be, as slash v. stab, as it is highly dependant on the situation. An attack directed towards a limb, with the intent of repelling that limb, is best delivered as a slash, as it is quicker, and allows your knife hand to fluidly move back to a defensive position, or to attack again. Such repelling strikes would be fitting for situations such as a gun grab, or the attacker having hold of your limb or clothing.
When the opponents attack is more direct towards your person, such as a tackle or shove, then a stab is more viable, as directed into the opponents torso. For one, it places your weapon and arm in between you and the attacker, with the direction of force directly opposing theirs. This collision of forces multiplies the strength of the stabbing attack by forcing the opponent to 'run into' your knife. Also, having your arm between the two of you puts you in the position to follow the stab with a defensive shove, aiding to help take the opponent off their feet.
The 'shank', or indirect stab, is best suited for extreme close distance defense, where you would be unable to get your weapon arm in between you and the attacker to use an effective direct stab. This is where I beleive an inverted, or icepick, grip really shines, as it lets you use your strongest core muscles to deliver a stab to your opponents back, aiming to hit such vitals as kidneys or lungs.
On having a weapon lodge, or become stuck into an opponent, is why the best targets are the softer organs, avoiding heavy bones which will trap a blade. It is why slashing the limbs is more beneficial than a stab, as theres nothing but bone underneath, so why dig deeper and risk embedding the weapon?
...damn you Mercop, dont bring up knife SD around me, Ill put someone into a coma with my rambling.
For reference on my veiws, I have my background in basic Kenpo karate, Aikido, Judo, and various military self defense tactics, and I have been through knife encounters. Just so you know Im not armchair ninja-ing.