The bad...many people make the mistake of pausing and exploding up then slowly coming down. This will destroy your knees. A lot lift way to heavy on these aswell.
The good again ...they can be great if you leave your ego outa it and put some lighter weight on there while controlling the movement through the entire movement slowly.
The ugly ....continue using bad form/heavy weight and you may not be able to body build in the future...at least on your legs.
Yours truely:Guy who's learned the hard way