I'm generally obliged not to give details as to what I thought of movies I've seen before they're officially released; but you may wish to take what you will from the following:
I am going to a midnight show of "Captain America." It is not a critic's showing or a free preview, it's a regular showing that I am paying regular ticket-price to see.
I am doing this even though I have already seen "Captain America," AND the "Avengers" teaser; for no reason other than I have an unignorable desire to see "Captain America" again.
I do not recall having done this for any other "big" movie released this summer.
Infer from this whatever you wish to infer, and make your near-future moviegoing plans accordingly.