How bad is it? It's technically crude (pun intended).
Should you see it? Certainly.
The Shaw Brothers made a ton of martial arts films and this supernatural thriller was usually only seen by those expecting it to be a chop-socky affair, making it almost a lost classic. A man develops the power to melt into a puddle of oil (which allows him to move faster, with fun special effects) and he uses this power to go on a killing spree. He's now impervious to bullets, but no one considers setting him on fire. There's one of the most awkward romances ever filmed as a subplot and I'm not sure how much of that was intentional. It's fast-paced, it's ludicrous, it's fun and it's about $4 a gallon.