The AMP version of the site is (as expected) not as performant as our custom optimised one. AMP version will load 1.2MB+ of data with 28+ requests, while ours makes due with half of that and 0.6MB with 17 requests. Some of that is due to AMP components that could be a bit more optimised (like we have a hidden youtube video that launches on click - and the youtube AMP component will load all of it dependencies on first start which is not ideal - our custom version does this when the user clicks/launches the video).
However - the new site release did wonders for SEO. Its probably not all due to just having an AMP version, but also just having a good mobile/optimised site - we still landed on 1./2./3. google search page results for some fairly generic terms. Really surprised us - kind of shocking actually, especially since we did little with the page before and didn't have that many inbound links, etc...