I've often wondered whether the problem with aftermarket polyurethane bushings not the fact that they're made from polyurethane, but that they're made from the wrong polyurethane. The traditional suppliers of these PU bushes have always skewed their products toward the performance buyer. The result is a vehicle that's hard to live with on real-world pavement. I'm sure there are lower-durometer synthetic materials -- PU or otherwise -- that could be cast from the same molds. Unfortunately, supporting a second product line called 'street' would cost a lot of money. The 'performance' segment of the market is, arguably, a lot bigger and certainly more lucrative.