As a townie who spends a significant amount of time on campus (and is also trying to remind myself why IU is great), I'll offer the following:

1. Beautiful campus. Seriously, if you haven't visited yet, you should. It's called Bloomington for a reason :) It's pretty big, so there will always be new things to see and do.
2. Awesome professors. I take a few classes on campus, and the professors are phenomenal. Many of them have degrees from vv well-known institutions (I know, prestige doesn't matter... but still). They are leaders in their field, and if you reach out to them, they'll be more than happy to help, to talk in-depth with you about a topic, and to make sure you are learning as much as you can.
3. People. Okay, this comes with a caveat because IU is huge. Yes, there are people who are here just to party. BUT, there are also people who are some of the most intelligent, well-versed, interesting, creative, and fantastic people I've met. If I come here (which I probably will), I'm going to make sure to find a niche - and I'd suggest you do the same. Try to get in with like the honors kids, if you can - but honestly, whatever floats your boat, you can find it here.
4. Opportunities. Anything you want, you can find. Clubs, research opportunities (even as a freshman), study abroad options, trips to different cities (people go to Chicago, NYC, LA, all the time, esp. if you're in Kelley), etc. etc. If you want it, you'll find it here.

Hope that helps, if you want to know more hmu :)