We have traveled several times to and fro, Mumbai-Pune and most of it being with MSRTC. The service is quite nice.
You can book tickets online and the prices are same (except additional convenience charge) even if you take the ticket on arrival (which is not the case with other travels). It stops at the Food Mall which I prefer, and again it isn’t the case with other travels. They are fast too and the seats are pretty comfy.
The only problem is that if you are not alighting at the start or if you don’t have reservation, then it’s difficult to find a seat in the front as buses get very bumpy and uncomfortable at the back.