A: Lots of Mailwizz/Acelle/Sendy users buy this product. We get feedback on the things customers want that are missing from our product which they're used to having in the other one they use, but overall the reaction is that they expect us to eventually become the consensus go-to self-hosted email platform due to a far better user experience and the overall quality of our software.

I'd recommend starting by just casually flipping through the docs to get an impression of the difference:

https://docs.emaildelivery.com/docs/faq/appsumo-select-faq