I tried VM and gave up becuse it was buggy and quite complex and comfusing to properly set up.
I tried Rockquickcart, and I found it buggy as well as lacking many features.
I also tried Open Cart, Simple Caddy, and many other Open Source carts as Prestashop, hopping to succed on bridging them into Joomla.
None of them worked with the feel and ease Ecwid works. Installed in 1 minute? Working nice and smootly, no problem whatsoever.
Resuming: Fool-Proof, nice looking, hassle free, no programming skills required... a jewel!
Without doubt the best and easiest shopping cart so far.