I know this was a thread a while ago but I was looking for some input before I added additional code to my product pages.

Which is best Microdata, Microformats, or RDF; specifically for E-commerce?

From Google Webmasters:
Products - Webmaster Tools Help

Microdata
<div itemscope itemtype="http://data-vocabulary.org/Product"> Brand: <span itemprop="brand">ACME</span> Category: <span itemprop="category">Heavy objects</span> <h1><span itemprop="name">Large all-purpose anvil</span> </h1> <span itemprop="photo"><img src="http://anvil.example.com/anvil.jpg"/></span> On sale for <span itemprop="price">$99.95</span>. <span itemprop="description">If you need an object to drop from a height, the classic A23859 anvil from ACME is the way to go.</span> <a href="http://anvil.example.com" itemprop="url">Anvil details page</a> </div>

Microformats
<div class="hproduct"> Brand: <span class="brand">ACME</span> <span class="category">Heavy objects</span> <h1 class="fn">Large all-purpose anvil</h1> On sale for <span class="price">$99.95</span>. <span class="description">If you need an object to drop from a height, the classic A23859 anvil from ACME is the way to go.</span> <a href="http://anvil.example.com" class="url">Anvil details page</a></div>

RDFa
<div> <div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Product"> <span property="v:brand">ACME</span> <span property="v:category">Heavy objects</span> <span property="v:name">Large all-purpose anvil</span> <span property="v:description">If you need an object to drop from a height, the classic A23859 anvil from ACME is the way to go.</span> </div> <a href="http://anvil.example.com/" rel="v:url">Anvil details page</a></div>