He looks awful - just states the fact He's looking awful - implies that normally Bill looks very well e.g. He's being so rude! means that he normally is very polite.

The present simple has a few uses but here it's used in the sense of "universal truths" For example: Water boils at 100 degrees. Monday is before Tuesday. And also for what the speaker sees as "truths"... For example: South Americans are warm and passionate people. That might not be true in fact, when a speaker uses the present simple, they're saying that's THEIR opinion of what is true. So, when you say: He looks awful ... the connotation is that he looks awful at the moment, and he usually does, that's how he is, that's his style ... he (usually) looks awful. You know that -ing is user for action happening now... I am typing. You are reading. So, "He is looking awful" means the speaker thinks the "being awful" is just happening now -- NOT "always true/truth"... HE LOOKS AWFUL ... usually, what a slob, he always looks bad... HE IS LOOKING AWFUL ... just at the moment, I wonder what's wrong, I hope he's okay...

The present continuous is used for expressing an action that is happening right now : I am reading (now). I am writing this answer (now). I am reading a poem (now). The present simple is used for expressing a general truth: My shirt is green (it is always green). The sun is hot. I like poems. The girl is wearing a green dress (now ; present cont) <---> The girl is beautiful (general truth ; present simple). The cat is running (now ; present cont) <---> The cat likes milk (she likes it anytime, in general ; present simple) .