Hi Guys, on 14th Oct 2017 I have made road trip to Nagpur from Pune in my car. Here are my some observation which I suppose would help you plan out your journey in due course.
Caution: Try to leave Pune by 5 AM or before if you want to beat enroute MIDC traffic & I am sure you can be at Nagpur by 16:30 or 17:00 HRS max. I left Pune at around 5:30 AM & reached at 17:15 in my home.
Pune to Nagar ------> 4 lane road & you can keep your speed between 80 to 100 max.
Don't take Nagar bypass instead take rode within city---- It's in horrible condition. Suggested by another fellow traveler. Thanks mate.
Nagar to Aurangabad -------> Good road but Aurangabad bypass was closed when I passed through this city but didn't face any traffic cause of morning time. Well you have McDonalds in Aurangabad but it opens by 10:00 AM.
Aurangabad to Jalna ------> Good road with minor potholes to surprise you.
& Now troublesome section of this journey starts when I crossed Jalna & headed towards Karanja-Amravati via Mehkar as this entire stretch is single lane & very badly maintained & you have small towns enroute which entirely sits on the road thus making your movement bit slow. Well you will see lots of speedbreaker on this section. Wondering why these PWD guys have built them.

But once you reach Amaravti then you have dedicated 4 lane highway till Nagpur with average speed of 100KMPH.