They definitely do disrupt flow, not only at peak times, but also at times where traffic is [supposed to be] moving nicely. I had to take the Ike from the city to 88 for years as my commute and there is something about a left lane merge and exit that turns common sense upside down. I believe they've also done studies that confirm this. Also, as mentioned, it's already been proposed that they move the exits to the right, multiple times, and when they proposed this, they had data to back up their concerns. I just want to see them replace the major intersections in Chicago with mega Euro-style roundabouts.... That would be fun to watch. Another idea that clearly works in theory but can be defeated by the American driver in no time.
However, the problem with the Ike is if you alleviate one bottleneck, you'll just be creating one downstream. No Mannheim backup inbound? The increased flow will find a bottleneck further down. No Austin backup outbound? The increased flow will probably find a bottleneck at the split (or I should say it'll make it worse). In the end, we're all fucked any way you slice it, it's just now we'll be paying for the privilege with few decent alternative routes.