We recently moved to Mailtrain for the Citationsy newsletter after hitting 10K users and not having sent a newsletter from MailChimp for a couple months (basically since we hit 2K users, the limit for the free plan). We now use Mailtrain with Amazon SES and it costs less than a dollar to send one issue of the newsletter, as opposed to $250 on MailChimp.
I can absolutely see the value in MailChimp, their editor is one of the best and the tools and ease of use are second to none, but the dirty secret is that you can still build your email in MailChimp, and then simply export the HTML and send it with Mailtrain.