... I had one student drop CS when we switched to C++ because she did not like it. But yes, on the final exam the Scheme students who did only a few weeks of C++ wrote better C++ programs overall than those students who did not do Scheme. It was the design recipe that really helped.
This year my students did not like Scheme as much, but on the final exam most solved a new problem and applied the steps better then in past years without the design recipe. I have also learned that I need to spend more time grading the planning part and less on the code. Those who had trouble in latter chapters were those who fudged on the planning on easier stuff.