Thank you for sharing your experience. It's bad because I like P2Pool, like the idea of distributed mining because it's not attackable with DDOS like other pools and there is not chance that pool operator can be disonest!
But if it works in this way it's unusable... In the meanwhile I returned to bitminter.com

With my 7970 I generate something like 5-6 shares a day. But at beginning it was ok, it was profitable, now it isn't anymore. Do you have latencies so high too?