I have been following this thread for awhile. Currently I use Product Designer even though my degree says Industrial Designer. I do this for a pretty lame reason. Basically when I graduate I would say I was a Industrial Designer and then get the immediate question so you do factory HVAC. So this became to long of a conversation for me to explain that is nothing like what I do. I found Product Designer was easier for people to understand and lead the conversation to a point that was more manageable. Not really a deeper meaning point but this is why I choose to stay with Product Designer even though at the company I work for they call me a Category Designer. Which is accurate for what I am doing for them. But I still refer to myself as a Product Designer outside of work.