I’ve been spending a hell of a lot of time coding Magento recently, and for any full time serious ecommerce business I would recommend a Magento solution. However I have spent much more of my time coding osCommerce and usually CRE Loaded osCommerce based ecommerce sites.
CRELoaded is still a great package (once you get rid of the annoying nags and ads) and is really taking the osCommerce platform and polishing it up to a nice usable fully featured system. If you are looking for a UK based developer who specialises in ecommerce, osCommerce and CRELoaded development then definitely get in touch. Don’t be surprised though if I mention that Magento is definitely worth a close look!