Yes, I'm finding this interesting too. It's an eye-opener that the 'Big Boys'. such as ACIS and Parasolid are both struggling a bit with this one and MoI seems to be taking it in its stride. I assume that as they can't radius this part much beyond 2.4/2.5 they must be hitting some kind of natural limit within the geometry.
If that assumption is correct, then does it mean that MoI's Blend tool is making some subtle changes to other parts of this solid that ACIS and Parasolid wouldn't consider to be acceptable?
I'm not trying to whip up an argument, I'm just wondering why there's a difference.

Martin.