Guys, was able to install the greasemonkey script on Portable Firefox 2.0.14 I have a lot of extensions. on my Athlon XP1800 with 1.25 GB of ram my google reader is getting slower. It seems that your alghoritm has something to do with how old is the post. Because most of the time I am getting a 1.0 score which is anoying. Also not sure if your alghorithm is able to deal with feeds in other languages than english. I am a romanian native and follow a number of romanian feeds which at world level are insignifiant but for me are very interesting. Maybe some learning options for your software (learn my habbits) would be very suitable. Looked at what I starred, shared or tag in the past and then adjust the algorithm.
For a guy who goes through more than 500 posts per day this kind of extension would be perfect if is functional. If you do not have already that info I can give you the XML with the feeds I read.