Thomas wrote a post about the Google Reader, so I thought I'd give it a try. As usual with Google services I was positively surprised, and have more or less switched to it now.
On the down side (as Thomas mentioned), I cannot easily see how many posts are unread, and to which category they belong - I have a couple of different categories, such as "Read now", "Read later" and "Read whenever".. I hope they'll add this RSN.
The big plus, is that it actually keeps the posts marked as unread until I click on it. In Bloglines I'd usually click on one of my categories, and all unread posts in that category would be displayed - it could be up to 40-50 posts all displayed at the same time - if I'd accidently close this page, or if firefox would crash (yes, it does happen once in a while) - all the posts would be marked as read, and it'd be a pain to read them.
Also, the Reader interface is sexy ;)