Hi,
I only have one L lens, the 24-105. My other two lenses for my 5d2 are a 20 and 40 from Voigtlander. I would not worry about whether my lens was a good or bad copy, I think that there is a bit of paranoia online about this, it is probably exceedingly difficult to buy a BAD lens these days. That said, my 24-105 does require a "minus 10" in the AF microadjustment (see the other threads on this subject). That adjustment did improve the images substantially, and I suspect that you may find that yourself - it is fairly easy to do this.
Jean-Michel