Saw Avengers - Infinity War and I really enjoyed it. I would not have been able to understand or appreciate it if my son hadn't made me watch all of the prior movies.
Without disclosing too many spoilers, I was delighted to watch the Avengers (and their friends) go up against a truly worthy opponent. I loved the ending - it had an Empire Strikes Back feeling.
I think it would be great to just end the MCU series with this movie. Just end it. No sequels or anything. That being said, I know that that won't occur, so I am very tempted to just ignore all future Marvel movies and pretend that they don't exist (something I should have done, for example, when Matrix 2 and 3 came out).