The missing part came in for the hardware entropy source. I had it generate 5 MB of unwhitened data and ran ent on it. This is what I got back:

Entropy = 0.970410 bits per bit.

Optimum compression would reduce the size
of this 41943040 bit file by 2 percent.

Chi square distribution for 41943040 samples is 1708712.21, and randomly
would exceed this value less than 0.01 percent of the times.

Arithmetic mean value of data bits is 0.3991 (0.5 = random).
Monte Carlo value for Pi is 3.638902145 (error 15.83 percent).
Serial correlation coefficient is -0.016616 (totally uncorrelated = 0.0).

What this shows is a slight bias towards generating a zero a little bit more often than generating a 1. Still, when this is whitened, the result should be good enough to be a reasonable key generator.