Might be worth while asking ckolivas if the S3 binary he done to fix the stale shares filtering can also be used in the C1? I don't have a C1, but it might be compatible......
If S3 binaries run on the C1, my binary is compatible.
Are the S3 binaries still needed with the latest firmware? I'm getting ~4% rejected and ~1.5% stale on my S3's with p2pool
Yes, I use it with the latest firmware:
http://ck.kolivas.org/apps/cgminer/antminer/s3/4.6.1-141020/cgminerAre there any other differences with this binary and the one bundled with the S3 firmware?
Any chance the S3 update from 20141126 has this update?
Is there a way I can check to see if it has the fix or not?
According to their support site, the only difference is: "Modify the previous version cannot restore factory Settings bug." I have no need to restore factory settings at present, so I won't install it

You can & should still use ckolivas's cgminer S3 binary with any/all firmware releases to ensure optimal efficiency with p2pool, until they can be bothered to fix the problem. You can also send ckolivas a donation as a thank you for his fixing Bitmains laziness.....

Thanks, what I meant to ask is, are then any differences in the ckolivas cgminer binary compared to the bitmain provided binary other than the previously mentioned stale share fix. I think you won't think you have a need to factory reset until you have a need to factory reset. I have put them all back on the October firmware, and installed the ckolivas cgminer, all are back and running fine now, and I think you're right, a donation is in order!