I'm taking the Illinois Bar in February. Do any states offer reciprosity simply because I pass the Illinois Bar exam? Is it a case by case determination?

Reciprocity between state bars is usually awarded to "reciprocal states"; i.e. states that have agreements with each other. In addition, you usually have to 5 years of legal practice in your home state and be able to obtain a letter from the state bar in your home state that your license is in good standing with no complaints pending against you.

I attached a link to the Pennsylvania State Bar below. This shows the states that have recipricol agreements with the PA state bar.

As far as I know, there are no states that just give you licensure in their state unless that state has a recipricol agreement with your home state, you meet the experience requirement, and you are in good standing with the state bar in your home state.
http://www.pabarexam.org/Bar_Examination/Reciprocity_Information.htm

That sucks. I thought that if I was licensed in one state, I could get waived into the other state without having to take the bar exam again. Doctors and dentists usually get automatic waive-ins.

My understanding on the subject is that each state has a statute or a bar rule on the issue of reciprocity. While some states do share agreements, all states have there rules on the issue. Which means that if your state does not share reciprocity with another state, you can look to that states rule to see what it takes to get in. Usually, it is the same whether it is a state sharing reciprocity or not, with another state. Most states require about 5 years of practice and the requirement that you take the written portion of the bar exam again, and they waive the multi-state portion. I know there are a couple of states that offer almost walk-in reciprocity, meaning no tests, just pass characater and fitness, pay your fee and your in. Florida I know is almost impossible to get in if you did not originally take its bar exam. These are my understandings, generally speaking.