Foreword: I work as a web developer, and work in highly complex dynamic systems, specializing in UIs and system integration.
I've worked with both osCommerce and Magento. Magento has very good marketing engine, really efficient throwing around of buzzwords. Sure it says on the cover to use Zend Framework and MVC pattern. What's not to like? EVERYTHING. The implementation is crappy even at best. It's not true MVC as view components actually FETCH DATA oO;
I spent about 3 weeks to get an new store launched, and launch was even delayed. The same work, the same system could have been done using osCommerce in a week...
I would recommend Magento only to my worst enemy, even that might be slightly too cruel. The list of problems with Magento is too immense to even start listing ... But i do say: Put it to SVN, checkout to empty directory and try if it work ;)
(Oh, and the development documentation for Magento is complete hokus pokus marketing bullshit)