Yeah the critics will say you're missing the whole website experience (for example) if a web page has a featured section you might not get that on the feed. Another example would be forums, where RSS Feeds can't quite capture the whole new posts in old threads format that's crucial.
As said above though the areas they excel are:
a) Keeping track of a large number of websites quickly. For example if you like the Astronomy Picture of the Day - rather than visiting NASA every day you get it in your feed next to the news headlines, music news, lastest movie trailers etc.
Whilst you mention you keep open a few tabs, of websites you visit a lot (for example I still visit BBC News every day) there might be some sites you don't bother visiting but still like to know what's happening briefly for example maybe Engadget for technology news or something. Once you think of all those other sites suddenly you can start growing your feed collection and the efficiency of RSS really shines through.
b) The other area where feeds are great are for rarely updated sites - such as perhaps blogs. For example I like to know what's happening with the iPhone Dev Team but they only post a blog maybe once a week. It's not worth me opening that site every day just to check if something is posted but with an RSS feed, it will show me the update as soon as it occurs. I can do this for loads of other sites such as Myspace blogs for all my favourite bands etc and then when you've got 20 bands you like and other blogs, it's way faster than checking each one every day.