I like that it is an easy way to send out invitations with my own design, without having any technical skills! The customer service was great as well - they were always willing answer questions we had about creating our designs or adding extra items for us in-house before finalizing them (which happened more than once).
There are no downsides at this time but one of which could be pricing since you can't have multiple versions sent through your account unless there's some sort discounting going around somewhere? It has been really helpful so far because everything went smoothly from start till end when sending invites online/through email using their software.