I was recently at a guitar show and a guy there had a Kemper rig set up and he was getting ready to start selling his profiles to the public soon. By trade, he is a sound engineer for a living (not a studio engineer, but a guy who gets paid to analyze the resonant frequencies of various products and those sorts of things).
We got into a discussion about sampling rates and after testing the Kemper for several months, his conclusion was that the reason the low end lacks on the profiles is because the sampling rate is simply too low to properly translate the low end. For the high end, its perfect (as shown in the EQ graphs). But for the low end the sampling rate of the profiler itself needs to be much higher.
I dont know how true any of that is, because well, I am not an engineer. Food for thought though.
The food for thought is how this guy makes a living as a "sound engineer"!