I've used peat pucks almost exclusively (for soil application) and would say, anecdotally, there is certainly variability from lot-to-lot. I don't know what is varying. Maybe it's the PH of the media from lot to lot (I did not test this, PH tested the water though). For instance, this year I had used a supply of peat pucks from differing lots and the germination time delta between the lots is obvious and significant (everything else being the same). Makes for a PITA.
So, yea, they are a bit worrisome. Although, despite the varying germination times, the final germination success rate seems perfectly fine to me.
What would you consider a better way to go? Rapid rooters?