Memorial Stadium as a venue is pretty clean. As the home of the Fighting Illini football team, it's a great place to go to with affordable tickets. They pack the seats in pretty tight for a college stadium (nearly 20 seats to a row so if you're stuck in the middle, it's ahrd to get out). It's also a fairly long walk from the bottom of the stadium to the top seats. Seeing the Illini marching band perform is definitely a strong plus.
A word of caution... they only accept cash for food and drinks. Sitting near the Orange Krush section is awesome. They are noisy and loud. However, the fans aren't completely into the game. Don't get me wrong, they love their team, but it's not the best college environment I've been in. The basketball games are a lot more fun.