I have used Flypaper as it is part of the Lectora suite we use. I have made interactive quizes as well as simple Flash interactions that we wouldn't have been able to make otherwise. We don't have the resources for full Flash development in our eLearning courses.
I've found Flypaper pretty easy to use on the whole, you don't requre any scripting knowledge although a reasonably logical brain helps!. I have pretty much pushed it to the limit of what it can do for us but it has made quite a difference to even our most simple courses. Users have found the simple interactions good to use.
If you are thinking of using it there is a trail version you can try before you buy.
Thanks for the feedback. I have downloaded the trial version and will test it out. Do you know if you can import questions from captivate into it and if they are still trackable?