I'm a recent convert to Google Reader. I found that I just wasn't reading or using RSS feeds with external apps, while google reader just simplified the whole process for me.
Also the OSX theme for google reader is fantastic. Much cleaner looking than the default theme :
http://www.hicksdesign.co.uk/journal/
I also find the google reader is quicker to load and scan for updates than my desktop one was, but then again maybe thats just me and my bad choice of apps.
The ability to check (and mark things as read) feeds on the go is fantastic. Makes the whole concept much better.
micro