I travel to Beijing a few times a year and have always flown. However, recently I took the train (gao tie G train) from Hefei station to Beijing and highly recommend it. Actually, it's better IMO.
The fast train has the following advantages:
1. cheaper ticket price (about 800RMB return)
2. takes 4 hours all up and arrives in central Beijing. When you factor in an hour to get to Hefei Xinqiao and another hour to get from Beijing Capital
airport to central Beijing, it works out to be about the same travel time.
3. The long-distance G train is actually more comfortable, smoother and quieter than the plane.