That's right, but while block difficulty is rising fast, it's more of a gamble than a centralised pool if you're using hashrates where the statistically expected time to share is more than the statistically expected time to a block for the pool. But it depends on how long your window of opportunity is while your equipment is still competitive.

Here's the most extreme way to illustrate the risks. If you get all your best luck with shares early on in the useful life of the miner, and p2pool does too with the network blocks, then you will comfortably do much better than with a centralised pool. If it were the opposite extreme, and you get your worst luck with shares and p2pool has it's worst luck with blocks, then you may end up with uneconomic mining hardware before you have a chance for the luck to rebalance.