We've had quite a lot of experience using Amazon SES, as we run an email marketing platform on it. We run both our marketing and transactional emails using it for https://emailoctopus.com.

If you're already using AWS then I'd definitely look at SES. I appreciate the price may seem too cheap, but the service is now used by huge companies for their transactional emails, the likes of Netflix rely heavily on it. As long as you configure your set-up correctly with DKIM/SPF I'd be surprised if you ran into too many delivery problems. Also worth noting they now offer dedicated IPs, for a not too costly monthly fee.