The user interface, it's very simple but effective; all information about your customers can be easily found by you with just one click! There isn't anything I dislike at this moment - everything works as expected for me so far (but we're still using only free plan). This service has been used mostly during our events registration process when creating an event page or sending invitations via e-mail/social media channels like Facebook etc., also booking rooms inside hotel websites that require payment processing such us Booking.com website was being integrated into my own system without any problems while other services were not working well enough since they required additional plugins installation before integration could take place properly.- Event pages creation-, Invitation emails preparation,- Room reservation within hotels sites requiring payments collection.