- Web-based so when I read from home or from work I don't need to sync my feed list (or remember what I've already read).
- The blog reccomendations feature is awesome. Since it is all centralized and they can easily compare people's subscription lists, this is definitely a no-brainer for them to do, but something that is near impossible with a native client aggregator. My reading list has already expanded immensely.
- Seeing who subscribes to my blog. 1-click ego surf.
- Aggregate information like most popular feeds, new feeds, overall directory etc. Dave Winer has been improvising similar functionality with things like weblogs.com and the Share Your OPML project, but it always relied on explicit user interest and buy in. Bloglines gets all sorts of interesting data for free just because they have a kick-ass service that creates such data as a side effect. Don't make me generate and upload my OPML file... just manage it for me!
Then when you are reading a weblog you would like to read with Bloglines, just click the Subscribe with Bloglines button (or select the bookmark) and you should be taken to the Bloglines weblog subscription page showing information about the weblog and asking for confirmation. Note, you will need to already have a Bloglines account and already be logged in. Also, not all weblogs have RSS/Atom feeds and so Bloglines may have some troubles determining the RSS/Atom feed for the site you would like to subscribe to.