Disclosure: I am the developer of this plugin.
I developed this plugin because I needed a way to add my own sign-up forms for MailChimp to various client sites so users didn't have to leave the website to subscribe. I had a plugin for this before called Newsletter Sign-Up but I figured it could be done much easier.
I didn't like the "official" MailChimp plugin much either.
This is the result. I'm using it and loving it so far. Hope you will too!