What are the positive aspects of Karl Marx's teachings?
Karl Marx placed social conflict theory above all else, claiming that conflict of class (powerful vs. weak) always occurred to the detriment of the poor when capitalism was freely allowed. To that end, he taught that the proletariat should rise up and remove wealth and property from the bourgeoisie, allowing the state to control and operate all sectors of business for the people's benefit.
One of Karl Marx's most famous quotes is: "From each according to his ability, to each according to his needs." In a perfect Marxist society, all citizens would work for the benefit of all; those with more ability would contribute more work and time for the benefit of those without, for sick and old, and for children (who could not work at first). This would ensure that every person in the society had an equal share of benefits, and an equal sense of responsibility. In theory, this system would also ensure fair distribution of wealth and property so that no one person, family, or business controlled or hoarded an unequal share. Since every single working citizen has a stake in the collective outcome, and their own outcome is dependent in turn on the collective, everyone would put forth their best effort, thus benefiting everyone.
The division of labor, then, would allow lower-class workers to occupy the same status as higher-class intellectuals, since everyone puts the same work into the system. Bricklayers would not feel inferior to physicists, since both would know that they are equally valuable to society. This would also remove the stigma of working "menial" jobs such as fast-food or sanitation worker, and allow educators and scientists more leeway in their own work -- the pejorative of "not really working" in a labor-sense having been removed. This, in turn, would allow government to have only a supporting role in regulating and overseeing all parts of society, and (eventually) vanishing altogether as the system becomes self-perpetuating.