Great plugin. A few thing's I've noticed.
1) You have the following in your code:
- the backslashes need removing as it's being outputted in the rendered HTML.
2) When the window viewport is squeezed, like in a mobile device, the height of the "Like" button is causing the other floated buttons that succeed it to not drop down below it. It results in an unseemly gap as a button is unable to flow underneath it. I know this can be corrected by overriding the .css with a 'min-height' of 24px or above to the various .rtsocial-BUTTON_NAME_HERE-horizontal classes, but just thought I'd throw it out there anyway.
3) The twitter button is showing the post title in the 'title' attribute while the other buttons are not. The facebook button just shows 'Like' in the 'title' attribute on hover. I just thought I'd bring this to your attention.
1) Could you please add rel="nofollow" to all the button links so link juice isn't passed out of the page?
2) Would you consider a smaller sprite instead of the 56KB .png? I think using a sprite is awesome, but for those that just use the standard small buttons, an alternative smaller file would be great.
3) You could make your script even faster by base64 encoding the sprite .png directly inside the .css stylesheet, and using something like '*background: url(/rtsocial-sprite-image.png)' as a backup for IE7 and below. Of course, this assumes you've put together a smaller sized sprited.