Depending on your school/program, dressing styles varies...that being said, I respect professors who take the time to have a clean-cut dress sense/style. I remember this physics prof I had in high school...he was literally the best prof I ever had. Why? Because he had this no-nonsense thing about him; his clothes said it, his manner said it...his teaching style said it! And we had a great relationship...I might have been his only student with a great relationship with him lol...
In university, i had this asian prof who seemed to wear the same clothes twice (Mon/tues or tues/wed,...). But he was hands-down the best math prof in the department! the smartest too! and yes we had a great relationship too lol
The point I'm trying to make here is this: we all have our 'comfortable' people/profs/etc...those who don't stand out (those without tattoes, dreadlocks - which I want to get but don't quite have enough hair for yet , etc). For most of us, these 'comfort pple' are the professional looking people...no matter how much you may love your prof, you know that if he wears 'random/i-don't-care' clothes, then he probably isn't the very best in his field...every once in awhile though, it so happens that the very best do not care about their appearances as much as their fellow profs (who are more presentable but lack the spark of 'genius').
I personally dress how I feel. Since I started this whole 'waiting it out' thing, I've been wearing nothing but t-shirts and shorts; not really taking care of my dress-look. For our stage, it doesn't matter so much...but once I get into grad school (god pls help me get in) I'm going to be wearing slacks/dress pants 24/7. Its just me, I want to live in suits during my grad school exp so that when I get that job in finance/wall st....I will be comfortable...if I intimidate you...so what, you probably need to grow a set