What's your experience with Channel Separation?

Channel separation, and crosstalk, are measures of how much a channel leaks into another.  It's expressed in dB, usually meaning how far below the driven channel the other channel which should be silent would remain.

In digital recordings channel separation is infinite.  A 111111 on the left channel remains 0000 on the right. It's at the analog reconstruction or afterwards that channel separation starts to be less than infinite.

I was reading a review of a Luxman integrated which measured around 70 dB of channel separation.  You think, well that's a lot worse than many digital sources, which is true, but, in absolute terms that means that one channel which outputs 1 V would bleed 0.0003V into the other.

Of course, this is one of the alleged benefits of mono block construction.  With separate chasis, power supplies and power cables we assume the channel separation to be infinite, but, honestly, with LP's providing far less than this often, does this value even matter after say, 60 dB? Have you heard this spec matter to you and if so what did you perceive?