Many of my friends have asked me which road they should use when going from Pune to Goa ?
I drive to Goa with my wife and kid at least once a year from Pune and I always use the following route and halts.
Pune - Kolhapur - Nippani - Ajra -> Amboli ->  Savantwadi -> Banda -> Goa  North -> Goa South
Google Map Link - 
http://goo.gl/XroC0d
Things to remember when you follow this route
1-> McD Kolhapur is on  the 
Other Side of the road when going to Goa.
2->Its very easy to miss the Ajra turn on the NH4 so 
slow down as you approach the Nippani Ghat and keep your car on overtaking lane  of the road.
(Landmark - There is a place called Hotel Goa Ways bang on that turn )
3-> Just after Amboli ghat you will see a board and a Y cut indicating to take left turn to go to Goa -
 DO NOT
 take this road . ( That road is very bad and my car got underbody hits 
at many points. Also its is very lonely route and not marked on Google 
Maps.) . 
Go till Sawantwadi  and then follow the directions as per map. 
Here are the 5 reasons I take the above mentioned  route :
1->
 Road till Nippani is NH4, mix of 4 and 6 lanes. . Quality and Traffic 
till Kolhapur is ok-ok but after Kolhapur  its very smooth. 
2->
 Ajra road does not have heavy traffic . You can find ST buses but very 
less number of trucks . So movement of cars is easy.
3->
 Amboli Ghat is just run down while going to Goa. That means you get 
only downhill when going to Goa and only uphill when coming from Goa. 
Ghat section is only 17 KM
4-> There are good places to take breaks on this  route .
Mc Donalds (Kolhapur ) -  Why ? - Hygienic food and Clean Washrooms .
Hotel Minerva (Ajra) - Why ? -Good food and  Clean Washrooms .
5-> No dangerous and high speed breakers  on this route.  You may find some small ones when crossing the villages. 
Important note :-
I
 have never  driven at night via this route and I will not recommend to 
take this road at night time as the road passes through some forest 
areas. 
I have heard that  Amboli road close down in 
heavy rains due to land slides at Amboli  section. So if someone is 
going in rainy season, better talk to Hotel Goa Ways or Minerva Hotel  
before reaching that far .
Drive Safe  - Not Fast ....
All the best. ...