Inventor Fusion has a little symbol that only appears if an operation or command has failed. If there isn't a problem, nothing is indicated (1st image). If an operation of any kind fails or runs into a problem, the little icon shows up (2nd image). If you mouse over the icon, it will display a message indicating the problem (3rd image).

The icon showing up similar to this might be a good method to use, if this is implemented. The mouse over message sounds nifty (and maybe looks that way in the example), but in reality, it rarely tells you anything worthwhile. In the sample, it just so happened to provide an indication of what the problem might be, but in most cases it doesn't. Often it doesn't provide any helpful information as to where the issue is or why. Perhaps that's what Michael was referring to when he said that's difficult to do well.

Personally, my experience has been that if MoI isn't able to complete an operation, I'll know it by looking at it. In comparing Inventor Fusion and MoI, I don't find the error indicator in Fusion much of an advantage, but that could simply be due to the type of modeling that I do. (please excuse the 10 sec. example I made, I just wanted to quickly force a failure)