I'm PPl with 250+hours, IMC.
I still use the whizz wheel and will continue to do so.
It works, keeps your brain in the loop. Doesn't require batteries .
Can't see any reason for not using to be honest.Its very quick to use.
The plane I fly has GPS , I don't have a portable one myself though (feel I'm in the minority there!) but manually calculating things I feel is the best way to go.
For navigation whilst I input a flight plan in the Garman 430, I fly using radio navigtion as the primary method with GPS as a background check. Plus if you can see out and are not in cloud, visual references as well to make sure the 'picture' looks right.
I don't fly using dead reckoning but I do plan using that method so I have times for the flight based upon the wind forecasts for fuel management.