I don’t have a great sense of how it stacks up, in the general case, against Sendgrid/Postmark/etc. Maybe someone else on this forum who has more experience with the spread of available options could weigh in.
I’ve used it for transactional emails quite successfully, but I can’t speak to deliverability with marketing email (which is where deliverability typically tends to break down, I think). I suspect individual mileage probably varies to some degree, but that you can probably build quite a robust and reliable system if you’re diligent about handling complaints and unsubscribe requests, you use DKIM/DMARC for message authentication, you protect your API endpoints, and maybe even use dedicated IP pools (if your app or user base is well established).
Here are a couple of resources about how to improve deliverability with SES (they’re not really an answer to your question, but maybe they’ll be helpful for folks using SES):