This simple plugin delivers exactly what it claims: the most important social buttons, loaded asynchronously so that they won't slow down your site. Very easy to install, with minimal configuration.
The only reason I did not give it 5 stars is that it offers, in my opinion, too little in the way of configuration options. For example, I had to hardcode my Twitter handle into the plugin in order to have the via @USERNAME attribution appear in tweets. If that option, and analogous settings for FB and G+ were added to the plugin options, it would be truly perfect. Many thanks to the developer for a useful and unbloated plugin.