Google Reader is fantastic. I've been using it for a few years now as my primary means of keeping up with sites I like - sites I used to actually visit on a daily basis, that is, before Reader came along. Once Reader got into the picture, it made it possible to get all the info for numerous sites in the comfort of a single, logically laid out and easy to use app (particularly helpful for dealing with poorly designed or hard to navigate sites). Nice!
So where's the downside? Advertising. For those sites that get some or all of their revenue from advertising, the loss of their 'regulars' to Reader is a reality. Before RSS hit the scene, if you wanted info from a site, you HAD to visit it, and those 'visits' translated into dollars. Perhaps this is why I'm seeing more and more websites now offering their RSS feed in an abbreviated, teaser format rather than full version. The message is clear. "Want the full story? Visit the site."