feedtree is somewhat like p2p for your rss feed. currently, each and everyone that subscribe to your feed will make a request to your host/server. one hundred subscribers, mean 100 request. that's eat up a lot of expensive resources (bandwidth & cpu of your server) which in turn you will have to pay higher to host your web/blog.
just like p2p apps that have no central server to distribute files/audio/video, feedtree will distribute your feed between all feedtree users. this mean, save bandwidth and thus save your money. also, this will speed up feed delivery to your subscribers. once a subscriber get your updated feed, all other subscriber get updated too. kind like 'push' rss feed.
feedtree works as a proxy server sitting between your rss reader and the internet. so, you can still use your favorite rss reader, you dont have to worry learning / using yet another rss reader.