Like I mentioned in my previous post:

If you want a CMS with a store on the side: Drupal + Ubercart

If you want just a store, I believe that Magento will be the way to go. I think that the clean store-specific admin interface of Magento is better than Ubercart's, eCommerce's, and VirtueMart's.

As mentioned in the article posted above, Magento will make an excellent osCommerce replacement.

I've put too much time into my friend's online store using Ubercart to switch - plus Magento in its current state is still lacking some fundamentals such as the 'Contact Us' form (on the roadmap, but should have been implemented from the outset)