I have used the Pop Up! plugin now on a few different sites. I am overall very happy, but I have a bit of feedback.
I think it would be helpful if you could use ids and classes in your html that are not so generic as to easily conflict with themes (such as BP Community) or other plugins. Using terms like "message" for an id or class has forced me to spend extra time adding html and css to my site to allow me to have better control of how the Pop Up! box appears. I would prefer to be able to hand over the creation/update of Pop Up!s to others, but while it works as it does, I cannot.
I appreciate your consideration of this. I hope you have a great day!
Ambrosia Web Technology