He's not too bad at it. He co-wrote Dragon's Din with Anne...wrote Dragonsblood himself...and it looks like they were back to co-writing this new one. He doesn't quite have Anne's style, but it's interesting to read his take on the Pern world.
Friends and I had long suspected she had co-writers even before they were credited on the covers, because the style had changed slightly. One thing I loved about her books was that they stretched my vocabulary as well as my imagination, and I noticed at some point they weren't doing that as much as they had been.