To re-cap:
1) Sharing AMP links is weird, feels wrong and Non-AMP links are hard to get
2) Breaks Safari's reader mode
3) Gives sub-par experience for websites that provide better experience when logged in since the AMP version is always the non-logged-in version.
None of those are deal-breaker for me because AMP pages come as a search results and fast loading results are very valuable for me when skimming to find the right one. Once I find it, I can switch to the full version(but Google makes it harder and harder. maybe this should be 4.).