Can't say I've noticed any problems - I've dropped the SNR to 3dB on my BE line and it seems virtually the same error wise as 6dB, but I have the first level of INP set as I was getting consistant PL on CQM without it.
Virgin Media 50Mb/s
53.34Mb/s - 1.65Mb/s - 29ms @ 24/05/2011
Andrews & Arnold
Speedtest to TBC