Meh. That could be said about it for the old location, but I haven't heard very many good things about it for the "new" location. Granted, I haven't been there myself yet, but there's a lot of empty space there, AFAIK. Maybe they've added some things since I'm been in college.
Honestly, I don't know of many great tourist attractions in Columbus, and I grew up here. The only one that I can think of that is nationally recognized is the Columbus Zoo. There's a movie theater downtown called the Arena Grand that opened in October 2001. It houses 8 THX certified screens, all with Dolby 5.1 surround. Although, I think it's one of those theaters that buys the fancy equipment but doesn't maintain it that well. That said, the presentation and upkeep of the theater is still pretty decent for the most part.
The Columbus Symphony Orchestra and the Ohio State Marching Band will be performing in an outdoor venue as they do annually at the end of July. This is the finale of the CSO's Picnic with the Pops series, which will feature fireworks at the end. Click here for more information.
You can check out CAPA's 35th Annual Summer Movie Series at the Ohio Theater. Here's what will be playing while you're there: The Godfather Part II, Alfred Hitchcock’s To Catch a Thief, Libeled Lady (1936 movie starring Spencer Tracy), Our Hospitality (1923 silent movie co-directed by Buster Keaton), and if you're staying the first weekend of August, E.T. the Extra-Terrestrial. Click here for more information.
The Columbus Zoological Gardens is a great idea. So big you'd really need more than one day to see everything, and last I was there it was a mere $5 adult to get in.
I visited COSI not two years ago; don't know how "new" that particular facility is, but the place seemed pretty well full to me. Of couse, any museum is always gonna have a section or two empty, getting ready for a new exhibit or something.
Columbus at that time of year is horribly hot and humid, so I second Thomas's recommendation of the CAPA Summer Movie Series. The Ohio Theatre is absolutely beautiful, and all shows are preceded by a 30 minute concert on the 'Mighty Morton' theatre pipe organ. It's a classy tradition and a good deal at $3.50/ticket.
Unless you're a prospective student or faculty member, I don't think there would be much reason to take a tour of the campus. I don't think there's much to see, but maybe that's because I've been around it so many times.