I have just installed and customised the mailmunch 'popover' free version.
Very easy step by step process.
Tees Fashion City
So far it sounds goo but I'm just setting up my store and don't know yet how it will work... I'll tell you more later when I know a bit more...
Foreal African Designs
I have only had the app installed for less than 24 hours so I don't have much to say except it was easy to install and begin using.
My connection with shoelace are not active with shopify .