it sounds like a good feature for CP to have. but what exactly do you mean by 40% bonus? is this compared to just sitting in an only BTC pps pool 24/7? do you mean hopping several merged pools or just staying on one? and with changing difficulty and exchange rates surly merged mining can't always give a steady 40% increase in BTC.
Yes, the 40% bonus was applicable at the time of my post. In the long term future the income bonus for merged mining will be precisely the market value of a namecoin divided by the market value of a bitcoin, maybe around 2%. Right now that is 28% and falling. In a small number of hours from now the income bonus will shoot up to around 100% (due to the falling Namecoin difficulty) but this will only hold for a day or so before returning to the mid 20's (my best guess).
That said, the income bonus should remain relatively high so long as the big pools don't use merged mining. This will pressure the large pools to switch and we will soon reach a stable point where most pools are using merged mining. I very much expect the proportional reward system will still be popular (why it's popular baffles me but it seems to be holding) so the miners which profit the most will be ones that have pool hopping software which takes full advantage of merged mining. I don't doubt that in the mid-term that pool hopping will dwarf merged mining in terms of income bonus but right now I think merged mining is more profitable than pool hopping regular bitcoin pools.
I personally have no desire for such software as I mine PPLNS. I just wondered whether or not hopping software could easily take both blockchains into account for effective merged mining pool hopping.