As to the necessity of conversion of CY and DECIMAL for OPC-UA, the behavior is correct. The design is such that all types are converted to CLS-compliant types so that any .NET programming language can consume them (CLS is Common Language Specification, see e.g. "What is the Common Language Specification?"). The fact that you want to transfer the types to/from OPC-UA is application-specific, and is therefore your responsibility to provide proper conversions.
I have to thank you very much for your fedback, and especially the difference between ReadItem and subscription which you have described. It seemed innocent at first look, but in fact it allowed me to discover a series of hidden bugs - mostly related to types conversions and especially with arrays, but also others. I have fixed them all, and the updated component and associated Bonus Pack are now available on this site (it is build 5.04.75.1).
With arrays, the proper behavior is to return .NET array of specific element type - not just array of Objects. For example, accessing "Simulation.ReadValue_ArrayOfCY" item is now giving System.Decimal[] (not System.Object[]) for both reading and via subscription. Note that this may need a change in your existing code, if you are relying on the old (incorrect) behavior.
I am also attaching the output from the enhanced ConsoleDataTypes example, showing how the various data types work.
out.txt

In the case of reading Simulation.Register_DISPATCH, similarly to the original problem with reading arrays, the initial value contained in Register_DISPATCH was VT_EMPTY, and this one cannot be converted to IDispatch, and that's why the exception occurred - in my view, correctly.
I have now changed the Simulation OPC Server so that the initial value of Register_DISPATCH is VT_DISPATCH, with a "null" interface pointer. This one actually works well even with your existing QuickOPC.NET build (and converts to "null" .NET object).
I have also added reading and displaying of Register_DISPATCH to the ConsoleDataTypes example in Bonus Pack.
Both these changes will be in builds 5.04.74.1 and later, which will be posted to this site soon, most likely during today.
support

Hello,
thanks for positive feedback. On my part, I would still like ot make sure that there is no problem with VT_EMPTY. Which item are you reading? Can you send the details of the exception? Are you getting exception diirectly in the ReadItem call, or in some code that is processing the result? Can you post that part of your code?
Thank you
Zbynek Zahradnik

I should add that the simulation server has been extended by new OPC items providing the supported types without a need to write into them first. For most part, they contain ramping values between 0 and 10; arrays contain 21 elements (0-20) that all ramp in the same way.