A large roadblock that I have encountered is the inability to pass parameters to sub-routines. This makes data-driven, and, more specifically, test-plan-driven testing difficult to accomplish. I suppose this can be considered a feature suggestion. Of course, if parameter passing is possible, I would love to know how.
Re: Passing Parameters...
You are correct, methods of the ODT objects cannot have parameters. In ODT, another approach is used: the ODT objects store the data needed for their methods to work.
So if you need to pass a parameter to a method of an ODT object, you need to write this parameter value to a field of this object and call the method.
This method will read the value using the following syntax: This.PropertyName.
Please let me know if you have any further questions.