I've been using it since the day they left private alpha, and this easy to maanage, efficient tool is such a cool way to keep track and comment on aggregated pages of other people's links, comments and data--think of de.licious, twitter and lots of other aggregators and tools all rolled up into one handy ball, organized by what people are willing to share in their feeds, and you've got the structure, with some additional bells and whistles added.
My own pleasure in friend feed makes it cool to see BizWeek's Heather Green do a piece on FF and the ex Googlers who made it (Paul Bucheit, Jim Norris, Bret Taylor and Sanjeev Singh.)
As Green so articulately says, the cool thing about friend feed is that it " isn't passive. Each subscriber can search, sort, or comment on the information in his feed. Thinking about seeing the movie 10,000 BC? Do a quick search on FriendFeed and you may find two colleagues who advise you not to bother. Want creative vacation ideas? Your friends may have suggestions."
After a few weeks on the service (my page here), and an ever expanding list both of people I follow and those following me, I'm most thrilled with the unique, real time features, such as the ability to post directly to the service and to comment on others posts and links. The ability to review stats and people looking at your own posts is also useful.
(I'm also waiting to try out the friend feed widgets that allow me to embed a selected list of data from my page and others onto my blog, web site, app, etc..if anyone has an example on their site, please send me a link, or leave in comments, below.)