The Shatabdi express trains depart from some of the bigger cities like Delhi and Mumbai and cover distances that take 6 or 7 hours. They are ideal for business travelers but tourists can also make good use of them by reaching their respective destinations my noon or earlier.
These trains seem to be very convenient and timely as well because I just checked and all of them start in the morning. There is very little time wasted if you travel by these trains and they seem to be very comfortable from the pictures that I see on the web.