My (pretty bad) experience with Schneider:
I bought the apo-digitar 35mm in 2010, and thought that the corners were pretty soft when shifted (probably due to field curvature, which is significant with this lens. Since I had read that this lens could be improved bei Schneider, I sent it in in 2011 (appr. 14 months after buying it) (via my dealer here in Vienna), along with detailed information and sample images.
They wrote back and said that the copal shutter was misaligned, supposedly because the lens had fallen down (which it didn't, at least not while I was using it). They said they needed to replace the shutter with a new one and charged me € 800,-, since the warranty was only 12 months.
After getting the lens back, I tested it again, same issues as before.
I sent the lens in again. Strangely enough, they now said that they actually had forgotten to replace the shutter, but would replace it now.
After getting the lens back again, I tested it once more, but the corners did not show any improvement.
When I wrote to Schneider again, they said that they could not comment on the soft corners, but assured me that the shutter was OK now. They also refused to refund the € 800,-
So, pretty bad experience from my side, I am very wary now and would probably look for a different repairshop in the future.
best,
geb