According to their test, which they did on the route between Shanghai and Beijing, the plane is still a bit ahead in terms of convenience. To be fair, this is about an 800 mile route, and despite traveling at up to 312km per hour (about 200 mph) the train journey still takes about 5 hours. According to our research, a 5 hour trip would lead to about 20 % share of the traveller market on that route.
Interestingly, the Economist does point out some of the marked advantages of taking the train though:
"So, in normal conditions it’s still quicker, if less relaxing, to fly. The train, too, is apparently vulnerable to disruption from snow. But it’s now a serious competitor—on price, comfort and reliability—to flying. And, as you race by rice fields and construction sites, you get to see a bit more of China, new and old."