payout stability of ghash.io, btcguild, eligius etc. is a myth.
The greater the proportion of the network hashrate a pool commands, the lower its variance will be.
That isn't a myth.
sure you get paid out with higher frequency, it does not mean that there is no variance.
sometimes p2pool does not make block several days and then makes 2 or 3 in wiry short time. daily payouts in other pools are day to day different too.
variance is a so to say "relative function" and depending what kind of timeframe you take as mirror.
it is not important how many payouts you have per day, week or month but its important how much BTC you get paid out in this timeframe. if you chose short timeframe you can speak about big variance. every longer timeframe that smaller variance. i don´t care (and for sure most of miners don´t) how often i get payouts, more important is how much i get paid out in the end.
of course if you have to sell your BTC daily, then it is easier to mine in some huge pool and enjoy this BTC or USD daily.
my variance i count per month and so p2pool did not disappoint me yet. monthly (income)variance speaks clear for p2pool.
of course it can be that small(er) miners have different experiences.