A good ending, definitely more adreliane pumping than the "everything is okay, everything's over" variation, but it definitely does decrease the epicness factor. Besides, it's not too suprising either;Hawkins getting captured and Valente being there is just really something you would except after watching 2 seasons of the show.
But still, it's exciting enough to make you want more. In fact, this ending beats season 1's cliffhanger ending by a mile, though, I would say that the show had better cliffhangers in regular episodes. Overall, it's almost certain now that the show won't come back, so I'm happy that the "conclusive" ending was aired; but I'm also happy we got to see the "what if.." version.