The line input is one of my favorite features of the Steelhead. I'm running a Weiss DAC1 directly into the line stage which renders some of the most seductive digital audio I've ever heard. As if it didn't already have enough variations for the phono stage, if you run the phono fixed out into the line in, you get a bump up in transparency and low end slam. The difference compared to the variable output is not small and I suspect the var-out has greater hi/low roll off. This creates an entirely different set of variables depending on the cables you use.
But to answer your question, the line stage is spectacular.