Here is my story:
A couple of years ago I was accepted to two top schools (I don't want to give out names) in my field of interest, theoretical high energy. One school excelled in phenomenology and the other in mathematical physics. It was a tough decision, and I waited till the last day to decide because I was so torn apart. In the end, I selected the school that is known for mathematical physics.
I attended the school for a semester, but then had to take a medical leave due to some serious health problems that came to light. It is now a year later, and I'm finally getting to the point where I can manage and deal with my illnesses and would like to return to studying physics. However, during my medical leave, my interests changed (my struggle with health problems has affected the way I view life). I spent a lot of free time reading current research papers in particle physics towards the phenomenology end of the spectrum. I now realize that this is the area of physics I want to focus on, and my initial graduate school decision was a HUGE mistake -- probably the worst decision of my entire life. The school I turned down would have been the perfect fit for me.
If I reapplied, what are my chances of being accepted to the initial school I rejected? Do schools hold grudges against people who rejected them? Would it be a waste of application money to even bother applying? I know I would have to wait a year to apply since I'm too late this year, but I can deal with that. Opinions?