I go into more detail in these posts [http://blog.trevorbramble.com/past/tags/googlereader] where I try to glue together Reader and Yahoo Pipes because Reader can't do even basic de-duplication.
Despite my gripes about it, it's the best available. (Though I'm sure their lack of improvements has a lot to do with that fact.)
There's a lack of keywords feed filtering, feeds personalisation, items expiration, some way to archive items for later and on and on...
My guess is that it's a very small team working on Google Reader and that they have the wrong priorities : the social stuff, at least it is for me.
I have to admit I was interested in exploring the social side with my app as well, so I'm glad Google made that mistake before I did. =^)
I just want a way to manage my river of news so that the can't-miss items aren't missed, and the always-skip items are skipped, and above all I should never be blithely offered the same exact link with the same exact metadata more than once. Everything beyond that is negotiable.