I've always been impressed with VM as one of the best e-commerce systems around, and VM2 continues to impress. Having been a user since it was Mambo-shop, I've seen how it's developed over the years.
With the experience of multiple sites built using v1.0 and 1.1 it was a bit disorientating switching over to the Joomla MVC model from the old themes approach, but having now built a number of VM2 sites I remain seriously impressed with it's flexibility and robustness.
Out of the box, the core functionality and styling are adequate (much better than the default themes for vm1.0 and 1.1 which were, frankly, pretty ugly), but initial configuration is quite complex, mainly because of the flexibility (read complexity) of what it will do. Other reviewers have commented on needing to know php to customise it - a bit of php knowledge is useful if you want to hack around the default templates and create your own template overrides (as is a knowledge of the Joomla MVC), but if you don't know any php / html and the default template doesn't grab you, there are plenty of low-cost commercial templates available as an alternative.
But a key strength of VM is that when you want more than the basic, it's there in the form of some truly excellent 3rd party extensions to deliver all the extra functionality you need. Many of these are commercial plugins, but mostly very low cost. Well worth exploring the extensions directory to see what's available. You'd have to be some cheapskate to begrudge a the few tens of dollars / euros it might cost to deliver the very fully featured sort of e-commerce site you can create if you want.
Where VM2 falls down though, is in it's documentation. Earlier versions, VM1.1 for example, had very comprehensive developer and user documentation, but this is lacking from VM2, where the online documentation is somewhat patchy.
I have road tested and built sites in other systems such as Magento, but overall, I believe VM is one of the best open-source e-commerce systems available, and remains my first choice.