You have to constantly fiddle with the "p=xxx" and it's not worth the hassle anymore; can't they arrange it so the sellers don't have to fiddle with it? Why would any buyer pay more for mining than buying a bitcoin directly?
This is why I don't point my rigs here anymore.
It's been suggested multiple times that if it was p=percentage and not a price then it would be easier for all.
IE: If p=5, then anytime the rate is 5% greater than standard it switches, all the figures are already computed by the site so it's not that hard to do surely