It's easy to use, it works for all of my clients - whether they are sending bulk emails or transactional mails. I love that you can easily set up filters if your client wants them as well which saves time in having to do so manually! There isn't anything at this point i dislike about deliverability tools but more like there could be some minor changes made here and there (maybe make the icons bigger). We have been able to keep our senders A/B testing very successful by using these deliverity checks. Their ease of integration with MailChimp has helped us get those results even quicker than before.