I don't think I mind this change. I mostly use my own mail servers, but when I setup a Discourse forum a couple months ago, it was so easy to turn it on with Mailgun that I gave it a try (the forum was migrated from an existing forum that sends about 9,000 email notifications per month, so I was going to be pushing the limit a little bit on the free tier right away). I definitely wasn't, and am not, willing to pay $35 a month for sending email for a forum I'm paying $20/month to host, and for a service I could setup in an afternoon on a $5/month VM, but if they want to charge me $8/month to send 10,0000 messages, I'm absolutely fine with that...the API, bounce processing, reporting, etc. are definitely worth a few bucks.

Mailgun was the obvious choice when I set it up, since it would be completely free for the volume I send, and I'll probably stick with it for that forum that's already using it, but now maybe I'll look around at the other options again for my next project.