As I have learnt, present perfect continuous should be used when we want to describe some activity which lasted for concrete period of time and is not finished still.
For example, "I've been waiting for her for 2 hours already" or "How long have you been waiting for her?"
These constructions (especially the question form, where 'have' cannot be shortened) look and sound rather complicated. That's why I wonder whether it's acceptable to use present continuous (especially in speech).
Another logical argument to use present continuous in question form is the analogy with questions which doesn't touch time aspects like:
What are you waiting for?
Who are you waiting for?
Why are you waiting for her?
How long have you been waiting for her?
So, is it acceptable to ask
How long are you waiting for her?
One more thing: does present perfect continuous add some additional hidden value, like expectation for results or anything else?