Dear Carinita,
1. �A key feature of this play is dreams�.
2. �A key feature of this play are dreams�.
 
My first inclination was to say that:
1.   �A key feature of this play is dreams�, is the correct sentence, because �A feature� is singular, so it takes �is�.
 
But then I reversed the sentences and had:
 
1.   �Dreams is a key feature of this play�.
2.   �Dreams are a key feature of this play�.
 
It seemed that 2,
 
�Dreams are a key feature of this play�, was correct.
 
Then I re-wrote sentence 1,
 
�Dreams is a key feature of this play�.
�Dreaming is a key feature of this play�.
�To dream is a key feature of this play�.
�Hallucinating is a key feature of this play�.
�Imagining visions whilst you are asleep is a key feature of this play�.
 
I convinced myself!  In my opinion, the correct sentence is:
 
1. "A key feature of this play is dreams".
 
I agree with Tech Teacher and Suha!
LES