Question: I was recently denied by the University of Pittsburgh's Main Campus, my first choice. I immediately requested to have myself reconsidered. If I send in my mid-year grades and score well on the ACT, what are my chances of being granted admission?
I can't quantify your odds, but the chances of overturning a denial are typically not good. If your mid-year grades and ACT score are significantly better than those you submitted with your initial application, then you may have a chance, but it will be a long-shot. So it's worth pursuing the appeal as long as, at the same time, you also pursue other options and, hopefully, allow yourself to get excited about the colleges that will welcome you.
Ideally, you can enlist your guidance counselor to help with your crusade. If he or she is firmly behind your candidacy, then a letter (or phone call) from the counselor to the Pitt admission office might have some impact, especially if the counselor can offer some specific reasons why you should be reconsidered. (Examples: your GPA suffered due to health or family problems or maybe you got stuck with several of your high school's notoriously tough graders. Or perhaps you are simply so charismatic, that you'll be a huge asset to the Pitt community. :))
But, again, don't get your hopes up. Admission officials have enough to do without having to revisit applications that they already reviewed. So your case may not receive any consideration at all. Thus, while you're waiting for your appeal to be resolved, check out this earlier “Ask the Dean" column about appeals and also be sure to read the thread it cites about satisfaction with “safety" schools. See Appealing a “Dream School" Denial and also http://talk.collegeconfidential.com/college-life/455645-experience-current-college-students-who-ended-up-their-safety-school.html
Good luck to you, whatever the outcome.