I'm a Kurzweil hater; sorry for taking it out on you.
The "technological growth is exponential" folks, led by Kurzweil, tend to use that to suggest that a timeline of future discoveries is predictable. That's why I have a cow over it.
Well, my take on the potential for a Technological Singularity is that it's called a "Singularity" because after a certain point the timeline of future discoveries is NOT predictable.
I agree it's incredibly difficult to put a metric on technological progress. However, I think it cuts both ways, against those who are certain the Singularity is coming, vs. those who are just as certain it'll never happen.
Another problem is that technological and scientific developments run way, way ahead of practical applications. Much or most of what we have now is really just applications of things developed in the 1980's or even earlier. Now we have prototypes of 3d cell printers, micro-fluidic labs, and DNA sequencers on a chip that hold the potential to do for liquids and chemistry/bio-chemistry that the IC chip did for computing.
Will all of these technologies that are at the same stage of infancy as when computers filled a warehouse and used vacuum tubes pan out? No. But it's also a very fair bet that some of them will.