AMP seems to contradict the idea that Google is invested in supporting the open web. And Google is a business, not a charity, they're not going to invest in something they can't monetize.
Here are mine:
I think AMP is a good thing for the mobile web. It makes web pages actually usable. People get a bit wound up about the fact that Google hosts the content on their CDN, but there is always a real URL backing it, the content isn't locked into Google's platform.
Overriding the default scroll behavior, so as to make the user have to scroll to the very top of the page to display the browser address bar is really annoying though.
Besides that, I often do prefer AMP pages due to them loading faster and wasting less data.