I appreciate putting up a list like this. That said, I want to comment on one of the listed drawbacks:
> Occasionally, obscure email servers will block emails sent through us
I have a few years of experience running my own email server and I can tell you this is a major pain in the ass. When you send your email via a small email server (a server that sends a low volume of email), you will have constant issues getting mail delivered. Also, most of the issues will not be with obscure email servers, they will be with Outlook and Gmail. When you send email, you will never know if your email will be delivered to inbox, delivered to spam folder, or blackholed entirely.
Related:
> We're not a suitable platform for sending marketing emails (although you should use a dedicated marketing platform anyway).
Please explicitly ban people from using your platform to send "marketing email". Clients like that are going to ruin deliverability for your other clients.