Looking into RDI for our 3.5 yr old. We have done VB / ABA and floor time and want to focus on social/relationship, so looking into RDI. Our son appears to be high functioning and social remains a core deficit for us. I see couple of questions on here before. Would love to hear any feedback. There aren't any controlled studies on it but it does have one (biased) small study without control showing benefit for children (with higher IQ).
After 14 years of doing ABA, we added RDI. It's been a big change for me. But for my son, he immediately started responding to a more guided approach rather than such a directive approach. He responds more quickly to me. We are starting to make real connections. And its been amazing for his self-esteem.
I suggest you find a good consultant to help you during your beginning phase because it's difficult to change the way you approach things. I'm still struggling to change the way I interact with my son. We use Lynn Houle out of Seattle Washington. She was the third one I interviewed and she has been a great match for us. The RDI site lists the consultants.
The RDI for Young Children book has lots of good activities and I highly recommend it.
I haven't read any RDI but conceptually the theory makes sense. There are RDI certified consultants that one can find to provide parent training (we will be meeting one to find out more) - it isn't necessarily done by therapist as it is about developing relationship.