Have you added it to your sites yet? It's extremely easy to do. Think it'll make a difference in SERPs or other?
Add this to your footer, just above your /body tag:
Code:
<script type="text/javascript" src="http://apis.google.com/js/plusone.js"></script>
Add this where you want the button to go:
Code:
<g:plusone></g:plusone>