Needs an analysis of the effect of the payout scheme
Some basics:
It produces a sizeable variance due to the PoT idea.
The share aging+PoT would give the equivalent of a block finders fee if the reward was paid after the block was found,
since the highest difficulty share will be the block share, and it will be effectively the newest (or almost newest) share found.
However, since the payout is determined before the 'last' shares are received, using a coinbase payout, not a normal payout, the block finding share isn't rewarded in the block payout, but I guess much later in the next block, expected on average 1Nd later, and thus always expected to be rewarded quite poorly.
i.e. the shares that are rewarded the best are those just under being a block, not those that are blocks. Those that are blocks lose one payout due to the coinbase payout.
These shares sent to the pool after the work that was used to find the block was sent, but using the same work or still in the same block of the found block, would need special rules to be paid fairly, since they are ignored in the coinbase payout (about 2.5% of shares)
Meanwhile, the other 'standard' pool that uses a coinbase payout is Eligius, which suffered from a very high orphan rate.
That could have been because of poor code, using a coinbase payout, or both.
Edit: OK, having thought more about it, that above actually points out the failure with this Scoring+PoT payout system using a coinbase payout.
You can 'hop' it by changing your payout address each time a block is found.
The coinbase block payout is calculated prior to the block being found, so it will overpay all shares up to the last work used to find the block, and not pay any shares submitted after the last work change before the block is found i.e. the person who finds the block will be underpaid the most.
Thus if you switch your payout address each time a block is found (unless you find the block) you would be overpaid on the previous address.
The pool will have to actually reverse that overpay in each following block, so if you are no longer mining to your previous address, that reverse can't be done.
Edit2: the same is probably true of p2pool except the 'underpay' is never corrected and there is only one share underpaid: the blockfinder share that isn't rewarded in the block found, and that share doesn't have an oversized reward compared to other shares, unlike PoT does.
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