I bought a CVP 207 Last year. I find the polyphony to be a huge problem as soon as you layer anything. It doesn't seem to be a problem when your using the accompaniment.
I love the CVP series. However, this is definatly a problem. I have bounced around between different manufacturers over the decades,and have found Yamaha to be very durable. So I will continue to by their product. Hopefully they will get it perfect someday.

Regards,
Dennis