The idea for this plugin is great and I installed it today after reading about it in the Nieman Journalism email.
But immediately after activating it on my site transitionvoice.com, all the displayed stats for social networking shares reset to zero. This occurred for both TweetMeme and Share This, so I know it's not specific to one social plug in.
Fortunately, once I deactivated Headline Split Tester, my social stats came back. But at least on my site, there does seem to be a conflict between this plugin and the two different social media plugins I use. I'm guessing that HST might conflict with other social plugins too.
I'd love to use your plugin, so I hope you can figure out a fix.