China has the world’s largest high speed rail network and, if you are visiting the country, it makes sense to use it.
For those trips, where the flight time would be a couple of hours or it would take up to 5 hours by train, the latter likely wins by door to door time (not even counting possible flight delays).
Just last week, I took a train from Harbin to Shenyang and few days later from Shenyang to Beijing. Due to the weather, the bullet trains were not operating (at least this was the reason given to me), but the regular fast trains were quite rapid and comfortable too.
You can buy these train tickets online, but usually the sale ends 3 days before the scheduled departure. One option is to get someone from the hotel to go to the railway station to purchase the train tickets for you.
The process of purchasing them, especially around the Chinese holidays, is an experience of itself (if you do it yourself). I would rather have someone else to do it for me if possible.
All the trains that I have been to have had at least two classes of service and some have even three. The business class is the highest class of service on three class trains (economy, first and then business).
I have now taken trains in China a number of times. Last year, from Shenzhen to Guangzhou, Shanghai to Hangzhou and from Hangzhou to Ningbo and the above mentioned just last week.
The train stations in China are modern and the trains have always left on time. This past Monday, I even missed my train by arriving too close to the departure, but the price of the ticket was fully reusable against a new ticket. Had to switch stations in Shenyang though and wasted three hours in the process.
The only drawback of using the trains that I can think of are sometimes the fellow passengers who cannot stop yelling on their cell phones or clearing their throats throughout the journey. Using ear plugs to have a noise free journey would be a good idea to make the trip more comfortable.