My experience so far with two up riding is that I prefer to ride alone. The wife and rode from the valley floor to 10K altitude pretty much a constant ascent of twisties and I could tell the bike was somewhat impacted by the additional 125 pounds of wife on the touring seat. It was still fun though. Most of us are not going to be into agressive riding with a pillion on board anyway especially on a challenging highway.
The bike is AOK on the flat with her on board though. When she leans back into the sissy bar it seems like she is not there at all on a straight and level slab at 60-65 MPH.
The touring seat got no complaints from my wife.
