Recently we did a magento commerce website and saw its raw potential in ecommerce.
Magento has surpassed all other platforms we used earlier in its features like CRE Loaded, OsCommerce, Ubercart or Wp-Ecommerce.
Magento has not only got umpteen shipping calculators but also great apis to be integrated like USPS, Fedex and blogs, cms and also bank gateway modules.
I reckon using Magento for all the other websites.
The websites we were talking about are: one.goprolocal.com/magento