Magento is a neat cart with some nice features. If I were still new to online sales and e-commerce, it would probably be my first choice, but I'm not, and it isn't. There is one simple reason why not. Magento does not have good (or even decent) CMS features.

I use to think "who needs a CMS? I just want to list and sell products. I don't want to deal with the learning curve for a CMS." Then I started selling goods online. I created a (for the time) good website with good products and good prices with oscommerce. I had everything I needed, except customers. In order to get customers, your need traffic. In order to get traffic your site must be placed well in search engines. Your site won't get placed without either paying for placement / advertisement (which destroys your margins), or having good content. You can't have good content without a good CMS. So, if you want to make a living selling goods online, IMHO, you need CMS.

Now you think "But Magento is going to integrate with Drupal." Honestly, I doubt it will work. Before we set out to create Ubercart, I spent a great deal of time looking at the available options. I spent weeks planning what it would take to integrate a cart into a CMS. I looked seriously at Zen Cart and Drupal along with others. Integrating a stand alone cart into a CMS is a nightmare. We quickly decided that the correct thing to do was to start from scratch. Around the same time Ryan looked at integrating Vbulliten into Drupal. I have seen many examples of attempts to integrate carts into CMS's, integrate forums into carts, integrate CRM's into carts, etc. . . And I have never seen one work well. At best they are a hack, with one notable exception being CiviCRM. It works with both Drupal and Joomla. I don't know if it was designed that way from the beginning, but that is quite a feat. I tip my hat to the bad ass developers who pull that off!

To recap: I believe that in today's environment a cart is not a good cart without CMS. Integrating a stand alone cart into an existing CMS is extremely challenging. Magento is not going to succeed in integrating with Drupal. Magento is never going to be the cart that Ubercart has the potential to be because it doesn't have good CMS support. I believe that Virtuemart, or the E-commerce module for Drupal are true competition for Ubercart. Administrators lacking experience may choose to start with Magento, but time and experience will show that they are better served by a tightly integrated Shopping cart and CMS like Drupal. I guess we will see if I am right.
Peace,
Andy