I went to UIUC for CS undergrad and I can attest that it is a great program. And very difficult. I graduated near the top of my high school class, but I felt very average when compared with my peers in college. There are some very, very smart people in the CS curriculum at UIUC.

Another great thing about UIUC is the diversity. It likes to present itself as an engineering college (and rightly so, top 10 in many engineering disciplines), so it attracts many students from other technical areas around the world (India, Korea, China, Japan, Russia, Bulgaria, etc.). I'm plain old whitebread, but I was the only one in my study group for several years. It was a great chance to meet people from very different backgrounds.

Lastly, they just recently (2004) constructed the Siebel Center for Computer Science which is where they hold most/all of their CS classes. A very modern, high-tech building that can make any CS major drool. Not to mention the other buildings which surround it: NCSA, Beckman Institute, and Grainger Library (will become your 2nd home)

http://www.cs.uiuc.edu/about/siebelcenter.php