Why would you "obviously" need to address this with the principal? I agree with the many posters on here who suggested you give her a chance- the benefit of the doubt. She could be an amazing asset to your son's overall education, or not, but the reality is you just don't have enough information yet to predict this.
And unless, in the next few months, your child becomes so impaired by his teacher's approach/personality/style that he is literally getting sick with the thought of going to school, then I wouldn't attempt a switch then either. The reality is kids will have teachers, classmates they have to do group work with, and eventually co-workers and bosses that they don't exactly jive with, but that they nonetheless will need to adapt to. That is life. As long as he is learning and he has a loving and supportive family at home and possibly other supportive adults in his life (coaches, music teachers, etc.), he will be fine and perhaps learn some valuable life lessons this year.
Also, I hate to say it, but when I read the line, "other moms felt this too!" I cringed a little bit, because it clearly implies that "the moms" were all talking about this new teacher in a negative fashion, otherwise how would you know how anyone else felt about it? It sounds dismissive, presumptive, and gossipy to me, and I feel that is not only unfair to your respective children by introducing negative energy into the classroom learning environment before the school year has even begun, but it is also terribly unfair to this teacher.
On a side note, I grew up in St. Charles, right next to Geneva, and also lived there a short time as an adult with my own child. I still have family there. I know this area inside and out, and I'm afraid that my experience has been that far too many of the parents in this community feel entitled and deserving of "special" treatment for their children where it is not necessarily warranted. A lot of my friends that have moved away from this community, as adults, will readily acknowledge this aspect of the Stc/Geneva. I have also had adult friends that I knew growing up that stayed back and taught in the public schools there. They acknowledged the same about many of the parents. I'm not saying you are this way; what I am saying is that their is a lot of communal pressure to be this way. So, instead of joining the "other moms" in disparaging this teacher before you've even gotten to know her, do your kid a favor, and be the voice of dissent saying, "Hey, why don't we give her a chance? She could be great..."