I have installed VirtueMart four times. And got it working on two sites. but only for a while.
Two major cautions need to be given to anyone that wants to use VirtueMart.
1. You MUST NOT be a Joomla newbie
2. You MUST know php
VirtueMart has so many capabilities it is compelling to download and install. But, if you plan a major store, you will need to know php.
If you are considering VirtueMart because it is free, its not. It will cost you many hours and days. Their forum is filled with posts from many people pleading for help. Many receive "me to" replies and many with zero replies that are months old.
If you want VirtueMart, hire a consultant that has at least 10 stores in their portfolio (and go visit them first). It won't be free, but you will improve your probability of success. For me, I'm bagging VM - its too expensive.