I always enjoy a good fleuron rather than the "***". They can really add to the feel of the book, and are so easy to put in there:
Code:
<div class="SecBrk"><img alt="" src="../Images/fleuron.jpg" /></div>
<p>Next bit-o-the-story...</p>
CSS:
div.SecBrk {margin:2em auto; text-indent:0; text-align:center;
width:15%; min-width:25px; max-width:150px}
div.SecBrk + p {text-indent:0}
Note:
although I think the text-indent and text-align aren't needed for a div, I leave 'em just to make sure.
I've heard that some sub-standard readers 
don't support ".SecBrk + p" so you would have to give that paragraph it's own class if desired.
Even without the fleuron, a top margin of 2em and no-indent certainly makes it obvious that it is a section break. I don't think anyone (in their right mind) would put a 2em padding around the page that would absorb the top margin. On the rare occasions that a section break actually appears at the top of a screen there would be a little extra space, and the no-indent makes it obvious enough in my opinion.
edit: just had to add this example of some awesome fleurons! Can you imagine the mood of the book when you see these every so often?? (lol)
