osCommerce is like telling people TM3 is the best new trading script.
You need Magento. We have been working shopping carts for 12 years, last 17 months all about Magento. Been a rough ride, but any webmaster with more than 10 sales/day, good accounting and multiple websites, needs something real, like Magento. Not for nothing there's a commercial version for almost 10k/year too.
We built a couple last few months:
www.espressoshop.nl
www.ds-stunter.nl
www.scheermesjes.be
All Dutch though. We have many more, but these are pretty much what it is about.