The little ACDelco jack is OK for certain jobs, but the arm is so short its not much good for anything other than oil changes or tire rotations. You would have to get really creative (and dangerous) to use that jack and actually be able to get under the car. It will barely lift a car high enough to get it on a small jackstand at the jackstands lowest position.
I now have a Michelin jack that Sams sells. It has a fast action so it raises the car really quick for no more than you have to pump it. Its pretty nice and I think around $45-$50.
when it falls on you, that 20 bucks is gonna seem insignificant.
I got a good crafstman 3 ton floor jack and jack stand set for like 150 bucks.
I don't care if its a $20 jack or a $150 jack, if someone is stupid enough to lay under the car with it on a jack they deserve to die. People that do stuff like that help keep the gene pool in check.