And no, the slower miners don't see any negative impact, because we accept shares, and pay them for shares for (CurrentBlock) and (CurrentBlock - 1). If a block is solved every 600 seconds, it would take them 1200 seconds to have their new shares for a getwork become stale.
So if i understand correctly, slow miners will be subsidised from money of honest GPU users ?
Just asking.
No. CPU and GPU users both have the same chance of submitting a share that is no longer current.
It's a (on average) 1200 second window of time, which actually overlaps as it progresses, that a user (cpu or gpu) will receive credit.
It should allow for CPU users to submit valid shares, some percent of which may be old, but in the same regard, also allows GPU users to submit shares for the prior block as well, which balances out.
GPU users may get their payout reduced by the value of a single share when a CPU user submits a stale share, but in the same regard, CPU users would have their payout reduced when a GPU user submits a stale share.
In this case, "stale" meaning, a share for the previous block.
The rate of occurrence is low however, and negligible.
I'm sure I could track previous block shares to show the exact amount of old work being done, but I find it moderately pointless.