If you know of a better way, feel free to suggest it. Every other way I've seen is unfair to some normal miners.
The score-based method is not better, but it definitely is easier for miners to understand (and it seems to work well on Slush's pool), and is less confusing. It is also way easier to implement.
Also, a few general ideas :
* You wanted to put a fee ? Do it.
* If you do so, consider adding the tx fees in the rewards. We would be the first pool to do this at the moment !
* If you keep MaxPPS, please, please, write a clear explanation and/or a FAQ in the wiki. And announce when you'll deploy it.