I have thoroughly tested this. This plugin can cause wild swings in page load times and page load successes (i.e. errors). As interactions seem to take place on the fly with different social networks, you are held at their mercy. Sometimes, twitter is busy and that icon slows down your page, sometimes it is stumbleupon. Other times, icons not even selected in admin to load (the "more" icon specifically) end up getting requested in the page and can cause the page to not finish loading and time out. I have simultaneously, tested this on four blogs over a week's period, and failures and weak links appear and disappear at the whim of the plugin (or the connections it makes). On average a page that loads in under 4 seconds without this plugin, will load (if it doesn't fail and time out) in between 9 and 56 seconds with it and the following icons selected:
Twitter, Twitter (tweet), Facebook, Facebook (like), Delicious, Google Bookmarks, Google Reader, Google email, Posterous, and StumbleUpon. In my tests only the three Google icons and Posterous never, ever caused a single page failure. The rest, over time did. Other Icons not mentioned were ruled out from my tests as I didn't need them. THough that doesn't mean that Google and Posterous preformed perfectly.
I tested with other plugins (heavy), custom templates (with and without plugins) and standard wordpress with no changes.
It was a shame as I so wanted this to work, or to find a way to make it work.
I wish someone made a plugin that could generate all the code needed for a post when the post was saved in admin (upon creation), without any communications at runtime (when someone visits your site) with other networks, and minimal scripting and database queries at runtime as well. Lean and mean. But that is contrary to socializing I suppose. It takes time to have a 9 conversations with various parties while someone is just trying to view and read your blog page,
A bad idea using this plugin, on my opinion. But, as I have yet to find another solution, maybe they all are poor. Beware, and keep a keen eye out (over time) if you do try it.