Bad things about St. Bernards they are very bulky dog who takes up a lot of space in your house and car, a heavy dog who wants to sit on your feet, lie on your lap. They also lean their weight against your leg. They are also rowdiness and exuberant jumping when young, "separation anxiety" and destructiveness when left alone too much. Fearfulness or aggression in some lines, or when not socialized enough. Some stubbornness and/or dominance problems, especially in males. They are a heavy shedder. They slobbery and drollery. They have serious health problems and a short lifespan.

The drooling is from the big floppy jowls. Just imagine if your lips were that big and couldn't stay together, you would drool all the time too. St. Bernards were bred to be big, originated in Switzerland in the Alps.  They were needed to carry large loads through the Alps and rescue travelers.  The hip problems are because of the breeding to make them big.  Their body develops so rapidly that the hips, typically the back hips, never really catch up.  It is called hip dysphasia, which just means that the bone going into the hip socket is smaller than the socket or joint.  That causes the bone to bang back and forth in the socket and bruise the bone, causing severe pain.