P2Pool's payout tab displays the information pertaining to the entire p2pool network hashing at ~116 mH/s. At this moment, there are (at least) four p2pool nodes connected to eachother:

http://fairquark.dyndns.org:9650 ~800 kH/s
http://0x0a.nl:8372 ~ 1.5 mH/s
http://62.210.204.178:8372 ~ 4 mH/s
http://5.199.162.49:8372 ~ 100 mH/s !!

As you can see, the last p2pool node has 86% of the entire p2pool network hashing power! Looking at http://5.199.162.49:8372/static/graphs.html?Hour, miner qXZhMBQ8nxQ9pdV9iZXxiUtdmvVs9jiPNi averaged 50 mH/s over the past hour, almost half of the entire network.

It would perhaps be useful if p2pool nodes were more explicit about how to find this kind of information, but I'm not sure how accessible such information is for nodes amonst themselves..