If you're on p2pool, are you using the stock queue option (4096) or did you change it?
I'm very happy with the performance of my S3s on p2pool so far, my second batch is arriving today and will pointed at p2pool without a doubt.
Its just a better pool
I have been testing the queue set to 1 on a single machine, after 21 hours the results are as follows:
queue=1 error rate: 0.00086971453%
queue=4096 error rate: 0.00180255332 %
It is worth noting that both of these are impressively low, I'll keep testing with a couple more machines, but I'm 99% confident queue =1 is the way to go.