One of the biggest problems with subscribing to lots of RSS feeds (I have around 90) is duplicate content — a particularly interesting story is blogged, reblogged, twittered and linked to by many different sites that you read.
Having all your subscriptions in one service such as Google Reader or Tumblr should allow for some better organising. Perhaps they should add an intelligent feature which scans your feeds for duplicates (this could easily be done by seeing if multiple blogs link to the same page, contain the same heading or even image!) and group them together as a sort of summary.
This would be very useful!