I’m in the process of moving my Bloglines aggregation settings to Google Reader. The features that I like abou Google Reader that prompted this move are:
I can add multiple tags to RSS feeds
Reader shows you what’s new (and also what’s old) in all feeds or across tagged items: no more navigating complex folder structures
the list display is easier to scan when you’re busy
it’s easy to share feeds or individual articles
you can replace the traditional static blogroll with a dynamic list of hot topics (see What’s tickling my fancy at left).
If only gmail had folders too!