I have found a discrepancy in the way hierarchy works that explains a previously
submitted "works for me" bug: (http://dev.cmsmadesimple.org/bug/view/6066)

Given a simple 1-level hierarchy with three hierarchy items, and each item
having several product items, the products page has the tag:
{Products action='hierarchy' detailpage='products'}

TOP LEVEL:
Visiting the Products page, you will see the three child hierarchy items of the
top level.
$hierdata is populated with the three child hierarchy items.
$hierarchy_item is empty
Template = Hierarchy Report

CHILD LEVEL 1:
If you click on one of the child hierarchy items, the page will refresh to show
a list of child products of the hierarchy item with the following info:
$hierdata is empty
$hierarchy_item is empty
Template = Product Summary

The only way to obtain the Hierarchy Item Name for this page is to get the
$entry->breadcrumb from one of the products in $items.  If I use this breadcrumb
it produces a link to the Hierarchy Item Name...more on this below.

CHILD LEVEL 2:
If you click on one of the products in the page above, the page goes to the
Product Detail Page for that product with the following info:
$hierdata is empty
$hierarchy_item is empty
Template = Product Detail

The $entry->breadcrumb will give a link to the parent Hierarchy Item.

BREADCRUMB HIEARCHY ITEM LINK:
If in either Level 1 or 2 above we click the Breadcrumb Link for the hierarchy
item, it takes us to a page for that hierarchy item that is DIFFERENT from the
Child Level 1 page that got us here.

$hierdata is empty (even though there are child products of this hierarchy item)
$hierarchy_item is populated with the fields for this hierarchy item.
Template = Hierarchy Report

Summary of the Problem(s):

Navingating down the hierarchy drilldown to a product, and then using Breadcrumb
links to try to go back up the way you came, leads to a different page/template
for the parent hierarchy item than you passed through on the way down.  This is
very confusing for both developer and website user.

1. When clicking on a child hierarchy item (obtained from the link in $hierdata
array), it should go to a hierarchy page for that item using the same template,
Hierarchy Report, not Product Summary as it currently does.  This url should be
the same as the one in $entry->breadcrumb for any child Products of this
hierarchy item.  Currently the URL in $hierdata is differnet from the one in
$entry->breadcrumb.

2. The Sample Hierarchy Report Template does not output any fields from
{$hierarchy_item}.  If you click on a lowest level Hierarchy Item (from the
breadcrumbs) this template will result in a blank page because: $hierdata is
empty, when it should have child Products, & the default template does not use
the $hierarchy_item fields which ARE populated.

This explains the bug reported here: http://dev.cmsmadesimple.org/bug/view/6066

Suggested Solution:

1. For the Hierarchy Report Template $hierdata should be populated with both
child hierarchy items, but there should also be an array of child products.  Or
else a separate array of child products should be included.

2. The links to child hierarchy items in $hierdata should keep within the
Hierarchy Report Template instead of going to Product Summary Template.  They
should be generated by the same bit of code that generates the
$entry->breadcrumb so that the links drilling down will be the same as if you
follow the breadcrumb back up.

3. Modify the default Hierarchy Report Template to show:
- the current $hierarchy_item
- The child Products of the current $hierarchy_item in their own array ($items)
- The child hierarchy items from $hierdata
(This will save some bug reports and support requests.)