Mario,
Here is the link to my slides:
I appreciate your thoughts. Here are some counter opinions.
First, you are coming at this from the perspective of a person who knows how to program "with massive doses of C, C++, Shell, TCL/TK and Python." So, what you really need from workflow tools is something that provides you a clean API and you'll code the rest. Nearly everyone on this list is the same, but what about the large number of people who are not? Must we force them to learn how to code? At the end of the day, different workflow tools offer different user experiences because they have different customers.
Second, you should try Java. You might like it. I cut my teeth on C, but also love Java. ;-)
Finally, keep in mind too that while ICE and Triquetrum are both written in Java, they are accessible to other languages through language bindings, as Erwin says. ICE also publishes its services through a RESTful web API, can be run headlessly, or accessed through a web browser from a remote server. As Erwin suggested, you might find Jonah and Tracy's work from Kichwa Coders to integrate C python with the Eclipse Advanced Scripting Environment (EASE) very interesting. We already use EASE extensively in ICE for scripting, especially related to neutron reflectivity simulations.
Jay