The shader clock is there, but AMD runs it at the same clock as the rest of the core. That means as you OC the core, your OCing the shaders as well. Nvidia's 8, 9, and GTX2xx series allowed you to OC the shaders independent of the core. The new GTX4xx series has moved so much out of the core and into where the shaders are you don't get to OC the shaders independent anymore. The shaders are now run at 2x the speed of what would be the core. Nvidia now calls it the half clock or uncore or something like that. Can't remember right now.
The important thing to remember is that it really doesn't matter. As you pointed out your 5770 is faster then the GTS250, 5750, or GTS450. Who cares if you can't OC the shaders separate from the core? On the same note who cares if its a 128bit bus? As long as it performs faster then X card, I don't care if its powered by 3 hamsters.