I've used Virtumart for years and have had to hack-together some very delicate additional components to get it to function in a comprehensive way, ie. uploads, and tons of css code cracking for a more pleasing and customer friendly layout. Additionally, I had many customers 10% or more that encounter cookie conflicts preventing 'add to cart' with their chosen browsers which has cause me to quickly help them perform an off-line sale.
Ecwid is fast - set up the store and authorized.net gateway in less than two hours.
Ecwid is stable - off-site CRM handling, processing and tracking sales.
Ecwid is easy to design - click, click, save, done.
Ecwid is intuitive - Zero customers have called to ask how to buy something.
Since I switched over two weeks ago my store life has been a dream.
The only two features that I would add immediately is the ability to customize the emailed customer invoice so it uses less paper and uses a smaller font AND the ability to organize orders in the back end into product folders. This would help a great deal is keeping track of fulfillment.
Great job Ecwid team!