no data, just opinion... i dont like the idea of using chemicals to flush and dont really see a benefit to using them... back when i ran a real op i used to just water with, er, water to flush but one of my collaborators didnt bother flushing at all... he hit with full strength nutes all the way through to the end... the difference between his and my final products was negligible.
i think truthfully people have gotten into the idea of flushing purely because the idea of the nasty seeming stuff they feed their plants just doesnt make em happy... purely psychological.
also though, i think it depends on the ferts you are using... some things will make a noticeable difference in taste and such... such as DB's use of Apple Juice
basically, if you were using guano (shit) on your plants you wouldnt like the idea of smoking that, would you?