Here is a solution I have found works perfectly. I think it is good to the search engines because they dont respond to javascript.. but I am not sure. I still have my index page with links to the store, to redirect search engines. Again, not sure if it matters...
</HEAD>
<SCRIPT LANGUAGE="javascript">
<!--
window.location.href="index.php";
//-->
</SCRIPT>
Thats all I do. Its in my 404 pages as well. Its pretty transparent I think and so far everyone seems to be redirected without a hitch.
you can see it in action (or not see it as the case may be) at
www.obsusa.com/store/index.html