Implementation: we had our developer manage this because of the specific functionality we wanted on our site. Not too much time for him.
Customization: very important to us given that we are a fashion brand. We are happy with the final result.
Support: we had some questions and there were new features released right after we installed the app. Support was responsive (more responsive than a competitor we were comparing to), implemented the new feature without requiring more developer time, and that was a deciding feature in me writing this positive review!
It is important that an app developer takes pride in their work, and that appears to be the case based on our experience with this app developer team.