"Q: Why does my miner say it has found a lot of shares but p2pool say I have only found a few?!
A: The real P2Pool difficulty is hundreds of times higher than on normal pools, but p2pool essentially lies to your miner and tells it to work on relatively easy shares so that it submits shares every few seconds instead of every few hours. P2Pool then ignores any submitted shares that don't match the real share difficulty. By doing this, P2Pool can more accurately report your local hash rate and you can see if you are having problems with too many stale shares quickly"
Wouldn't that increased difficulty increase the luck of the pool?
Well, p2pool is opensource, and has been around for a good while. The author, forrestv, is a reputable member of the bitcoin community, as far as I can tell.
The meaning of the question you quote is that most pools set a share difficulty which is relatively low (probably somewhere in the range of 64-512 for KnC miners), and it sets your payout based on how many of those shares you submit versus others also mining on the pool. P2Pool doesn't work that way. It actually has its own block chain, and each block has a difficulty that is considerably higher than the traditional share difficulty, but still much lower than the bitcoin network difficulty (currently this difficulty is in the 300K - 450K range), and your payout is based on how many of those blocks you solve relative to other miners.
People mining on P2Pool typically don't have machines that are any 'stronger' than people mining on any other pool. They use the same hardware as people mining on other pools. The block solutions for the P2Pool blocks are harder than typical pool shares, but that doesn't have any effect on how many actual bitcoin blocks get mined by the pool.
I think this has already wandered way off topic for this thread, so if anyone has any more questions about p2pool, we should probably take it to the appropriate thread:
https://bitcointalksearch.org/topic/1500-th-p2pool-decentralized-dos-resistant-hop-proof-pool-18313