From the standpoint of a graduate student, advisors are supposed to be superhuman. We are supposed to possess supreme knowledge of all things technical as well as academic, but also be well plugged into industry, federal funding agencies, and miscellaneous professional organizations. At the same time, we are supposed to be master psychologists and instinctively know what the student needs, provide advising when needed even if it is not asked for, be hands off when the student wants to be left alone, provide structure so the student has clear goals towards which to work, but also not be too demanding or smothering and instead allow the students to enjoy life, hobbies, and have the hours they want to work...
But, alas, advisors are only human. They have all the flaws that other humans have. Some of them -- the evilest of advisors, I am sure -- apparently seem to possess the sum of all the flaws that all the other humans have ever possessed in the history of mankind...
Yes, it can happen that a professor, perhaps a potential advisor, simply does not like you, and for no good reason at all. You just rub him or her the wrong way. Because that's what happens with humans; sometimes they just don't like you. Advisors are not supposed to let it affect their professional relationship with you, but you can bet your sweet behind that whether or not they like you is a real factor.
One thing that I really don't appreciate in people at all (and graduate students are people) is being too cocky. I understand it's often a cover-up for insecurities, but I don't care. There's being confident, and then there's being in other people's face with all your perceived awesomeness, and I just cannot stand it. I hate arrogant people. (The fact that they are the ones moving fastest and highest in my discipline tells you that I am unlikely to reach stratospheric professional heights. But I have my distaste for arrogance to keep me company here in the murky waters of mediocrity.)
There is a new student who is currently TA-ing with another department and is considering joining the group. He is well-qualified and on paper looks like a perfect match for my group. But, he has been rubbing me the wrong way from the get go (which wasn't that long ago). I know he shouldn't, he hasn't done anything wrong, but he does. He seems annoyingly confident and comfortable, just completely unfazed by starting grad school and in a new country at that. Even my American students are more apprehensive than him about the new experience, let alone my other international students. The world seems to be this dude's oyster and I fear he is going to be really hard to coach, as the attitude is that he already knows everything. I am about to graduate a student with the same attitude, but even that student he didn't start as cocky as this new kid... So I am on the fence about accepting this student into my group. I probably have to get to know him a bit first, to decide whether he's worth the hassle. The funniest thing is that, being so awesome, I don't think it's even in the back of his mind that I might not actually want to work with him; as far as he's concerned, it's all about him making "the choice that's right for him."
How I hate the syntagma "I have to choose what is right for me/my family" cannot be described. It is such a pointless, bullshit phrase, and is terribly overused in some corners of the blogosphere; of course you are choosing what's best for you and not what's best for my college roommate's second cousin once removed. I hate that phrase about as much as the words "resource", "novel", "innovative" (especially when the latter two are used together), "program", and the word "impact" used as a verb. You know, like when we talk about how we are going to employ novel resources in our innovative program to impact broader audiences in novel and innovative ways (*shudder*), ways that were unimaginable without said resources within our freakin' resourceful, novel, innovative, and impactful program. Which is (obviously!) the best program you could possibly choose for you and your family.