According to emails I've gotten from current Cornell College students and chats (a senior at my high school last year is a current student), the OCAAT plan actually works very well. While it may be a little difficult for language majors (at least in my mind), it really helps with making students disciplined. You can't procrastinate, you can't distract yourself with other classes and use them as justification for falling behind in another class. Also, it seems that the scheduling, where the classes don't really go late in the afternoon, helps students who want to be involved with a lot of activities. They have time to do so.
I also chat with Terri on MSN, and she seems really fun and quirky. Knowledgeable and great to listen to a prospective freshmen's questions or even drift into general conversation.
I've attended a chat for admitted students and post sometimes on the "Cornell Connection" board (does your son?) and the incoming freshmen class seem to be
really nice, friendly, sweet, diverse and charming. Were you able to visit last week?
Unfortunately I don't know much about the life at Illinois Wesleyan, so I can't give you a balance feedback.
Either way, I think your son has two great choices! Congrats!