Been using this for over a year. Before this it would take literally hours of boring work to send out a newsletter with ZOO content. So I almost never did it. Now, it takes about ...1 minute and I have a regular newsletter schedule. I just create a newsletter in AcyMailing then select the ZOOmailing tag for my most recent article, ZOOmailing does the rest and adds the article to my newsletter.
I do with there was more control and customization options so it would look less boilerplate template-ish but I'm still happy. Totally didn't know they don't charge for non-profit sites because I just renewed. doh.