Wheels and saddle selection have lots to do with the way a particular bike rides. I have an all Al frame bike that does ride somewhat rougher than the steel framed commuter bike I also have. When you ride 700x23 pumped to 130+ psi, you will feel every twig on the asphault with most bikes.
I recently put a Brooks team pro saddle on the Al bike. I ride the same roads as before, with the same wheels and tires, but don't seem to get the same sharp bumps that I was getting before. I am happy with what I am riding.
I understand that some of the newer steel frames ride almost just like an Al bike. Is this true?