However, when I publish pillar reference content aimed at geeks, the simple Delicious button which shows number of people who already added it performs VERY well for me. (Incidentally: that social proof is totally missing with ShareThis/AddThis/etc. I wish they would incorporate it.)
Delicious also generates long term traffic, whereas most of the other social sites do not.
And just so we're on the same page, you're talking about this, right:
http://delicious.com/help/savebuttons
I just added it to my site but I don't see any option for displaying the statistics you were referring to - i.e. how many people have bookmarked something with it (except on the delicious website, of course). Maybe you're using a different button?
i feel like a better implementation of them would be something similar to how the digg button works. create some sort of widget that determines what networks you're logged into, and only display those buttons. that way, its not a wall of buttons, but a custom menu of the sites you're at least making use of as a registered user.