There is a great article at /usr/bin/geek about how Google Reader could easily kill Digg. I have to agree with the author when he says:
If Google Reader aggregated and displayed how many people shared each post and then calculated the most popular ones and displayed them in a separate label (like they have for stared and shared) they could have a feature that kills Digg!
I never thought about it, but this would definitely be an amazing feature. Another feature that I would love to see is the ability to search your shared and starred items. Either way Google Reader is still my preferred RSS feed aggregator, but with a few minor tweaks I think Google Reader could be perfect.