I just wanted to drop a note on how to stop the scroll to top link (button) from momentarily displaying when the page first loads.
Just edit jquery-smooth-scroll.php, and add style="display:none;" to the <a id="scroll-to-top"..... under "Core Functions"
This worked my for me. Stopped it from displaying for a second during page load, but still shows up perfectly once page is scrolled.
Note to Author: Thanks for including documentation/comments in code. This makes it SUPER EASY to customize the plugin!