Do Fast Lenses Matter Anymore?

Yes - totally agree.  Looking to break out of the ISO performance of my T1i, but it's less about crop vs. FF, and more about what leaps in ISO improvement mean - regardless of format.  My premise - right or wrong, is that it will be bodies and not lenses that offer value for speed moving forward.  I think the progression on ISO is fulfilling one of the biggest promises of digital - that light capture is going to get better and better and many limitations will go away.