I have been playing with it and I have mixed feelings about it. How have you been using it and do you have any sort of feedback?
Not be able to run script via Data API is an issue for me. One of the issues with with REST APIs is the lack of some transactional support. For instance changing an inventory qty needs to be done as an exact count and not as +2 or -3. This enters an issue where a busy system can have count issues if multiple calls update the qty in a short time period after all getting the same start qty. Yes there are ways around this issue but it is cumbersome.