Tires are designed for different uses and with different features and benefits. Occasionally, I will talk to a customer with a brand new vehicle, who after driving it for a while realizes he/she isn't thrilled with the ride quality of the O.E. tires. Usually the complaint is that the ride is too harsh, especially when going over bumps.
There is a post right now in the Club Lexus forum that is a good example of this common complaint. The owner of a 2007 Lexus IS250 with the optional 18-inch performance tires and wheels soon realized that the ride was too harsh. Why was it so harsh? The large performance tires and wheels gave the car a stiffer ride quality because of the lower profile. If keeping the wheels is preferred, I would recommend selecting a tire that is more ride-oriented. But the surest way to solve the problem is to downsize to a 17-inch Tire & Wheel Package AND pick a nice riding tire. This would increase the profile of the tires, and with more profile, the end result is a better ride.
And besides, this person likes her car. It would be a shame to get rid of such a nice automobile when there is a relatively simple solution to the problem.