IC Cards doesn't provide the functionality to express the messages from external user. For example, in my application, there are two messages sent from extern users. The first one is "Load Source Image" when user presses the corresponding button. The second one is "Run Segmentation". We don't know how to use IC Cards to record these external messages. It can only record the message that it will send to other IC Cards.
The second disadvantage is about the six colors in the IC Cards. I don't see much help from these color categories. Instead, it always incurs troubles because you cannot decide which color you should use to represent the IC Card in many situations. For example, it is not easy to decide which color I should use for my first IC Cards, "Main Control". Simply saying it is purple might not be a good idea since it doesn't make thing clearer.
By referring to the CRC Cards, I notice there are two important characteristic missing from IC Cards. They are "Physical Interaction" and "role-play". It is these two features, especially the latter, which makes CRC Cards attractive. Since IC Cards is very similar with CRC Cards, missing these two characteristics is not a very good thing.