the pool average is 11.8%.. so 5% is wasted. I didn't check, but it wouldn't surprise me if p2pool.org does have a 2% fee.
which goes back to Mike Hearn's post - people don't know how p2pool works so they'll just say "11.8% is wasted, lolz, [insert pool name here] is so much better and they charge a lower fee than p2pool charges" and they think p2pool.org is "The P2Pool."
It's unfortunate that p2pool.org doesn't present itself better.