This travel tip is based on my recent travel in UR coach of this train from Karjat to Lonavala which also was my first unreserved travel in any M/E trains.
Crowd: If you want to reach Pune in the afternoon and don't have a reserved accommodation, this is the best train. You can travel from Mumbai to Pune and even beyond while sleeping in the UR coaches. My UR coach which was the first coach behind loco and was the most densely populated UR coach with a total of 6 passengers on board.
Boarding:...
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As the timetable says, this train doesn't halt at Thane or Kalyan and hence you have to board at LTT or Karjat. Even after considering this, this train remains is a great option for UR travel. It trails the over-crowded Koyna Express up to Miraj and hence you can drop the option of Koyna express by taking this train and travel conveniently.
Coaches: The UR coaches are clean and very well maintained.
Railfanning: It travels through the Bhor Ghat and Shindwane Ghat sections in daylight and hence offers some awesome views. Try boarding the first coach and you would be in for a treat by the 'khatarnak' chugging of Kalyan's Shakti throughout the ghats.