UIS is a great university. The university is very student-focused. Professors and administrators (including the Chancellor) engage with students and it is unlikely for students not to have a professional friendship with professors if they seek it.
The programs at the university in the Political Science Department, and from what I have heard and experienced in other departments through cross-listing courses, are good. It is challenging to achieve the A, but if you want to achieve a B-range grade it isn't too difficult. For the academics of my program, I am glad I attended the university.
Springfield is a good city as well. It is not a happening place, but if you're looking for a stable small city to get your education in Springfield is the place (especially if you are seeking government internships in the diverse agencies the State has). The people are overall friendly. That being said, UIS is not in Springfield. It is in the middle of a corn field about a mile from anything except the community college. Having a car is a necessity, unless you want to rely on friends or the unreliable Springfield bus system. You are an additional 5 miles or so from anywhere of happening in Springfield (Downtown or Veterans Parkway). And the road system makes UIS in the most awkward part of the city.
The student body is small. You will definitely get to know most of the students in your major. Drama can run rampant, but there are definitely great groups of people that do not engage in that. It's a matter of reaching out and connecting with people. Student organizations are not terribly active but do regularly meet. Most organizations focus on politics or religion. Students are friendly overall as well, but not really actively seeking you out.
The university is very political in the liberal sense. The campus food is not good, so Chic-Fil-A was seeking to open up on campus in early 2012. But the LGBTQ community put up such a riot that the student government formed a committee of anti-Chic-fil-A people to decide the restaurant's fate on the campus--none. Additionally, if you're white you'll feel like your not valuable. But if you can overlook the university's "scandals" like that and focus on your education and your group of friends, you won't regret attending UIS.
The administration is also very easy to get along with and deal with. Just treat them nicely and they'll help you. I would have gone elsewhere for school, but I'm do not regret attending UIS. It's a good institution that has really opened my mind and made me a much more intelligent person.