It's very easy to use, has great support for all of our domains (including subdomains), can be used with any ESP or service provider that supports PHP/CURL API calls; they have some really nice features like multiple campaigns per domain so we don't get split out in different lists when sending emails from more than one account through them - it makes things much easier! I wish there was something similar about their autoresponders as well but other then this I am happy with everything else.
We've been using DnsExit since before launch date 1 year ago now and haven't had anything bad occur yet regarding the quality of work nor price. Easy setup process, quick response time by customer support team.