A number of months back I posted on the measurement of C1 error rates on various audio CDs I tested with my Plextor DVD drive. They have a utility on a PC (PlexUtilities) that will scan any CD/DVD for errors.
I found a large variation in error rates. Some have argued that C1 errors do not effect CD playback, but that the more serious C2 ones will. I am not so sure. I very rarely found any C2 errors in all the disks I measured.
I found some recently pressed domestic pressings to have C1 errors in the few hundreds, while my Japanese SHM CDs had a total C1 error count under 10 on the whole disk!!!
I also found somewhat higher error rates on older 80's pressings, but some recent pressings were as high or higher than these as well.
Unless the disks were dirty (I always cleaned before measurement), polishing the surface had NO effect on the C1 error rates measured.
If you are ripping, I also found the higher the measurement speed, the higher the error rates on the same disk. As a result I measured error rates at the slowest speed the Plextor would run at. I suggest you rip at the slowest speed as well.