From what I've heard from my mom, who used high speed rail to travel between Shanghai and Nanjing last year, the story of "half empty trains" was only valid for very early or very late departures. The trains are absolutely packed during any other time. Not that high speed trains don't have problems though. One of the main complaints was that the high speed trains stopped at too many stops during the Nanjing to Shanghai trips and the average velocity ended up being around the same as that of the "Dong Che". I think they've fixed that after the rail department got a lot of complaints.