Hey,
One question. I looked at the algorithm and it seems that you'll get paid extra credit even if you stopped mining. Is it right?
If it is so, is there a variant that miners that ceased their activity (did not submitted share for given round) will be paid last? I'm thinking of this because if the majority leaves the pool (honeslty, almost 200GH left the pool when bad luck broke in full), the others will be mining and paying them, and in the end it will take longer to get to positive numbers, leading to more miners leaving and sending the pool to grave.
If you'd delay those payments until every active miner has zero extra credit, those who are mining will more likely stay on the pool, since they'll be getting at least the expected PPS.
Also, isn't this problem in ESMPPS? The veteran miners might be motivated to mine under new address to get paid sooner.
I'm sorry if this is answered somewhere, as I haven't actually studied more to it than what is on eligius wiki. RTFM-like answer would suffice :-)