Honestly, it can be a bit of a pain to get setup properly at the start, depending on how well you understand spreadsheets, but once you configure CSVI properly for your needs, it works like a friggin' dream.
So save yourself the startup headaches and just get the Pro version, and the awesome support that comes with it. It's worth every penny.
I'll never even think about building another Virtuemart store without CSVI Pro. An absolutely MUST HAVE extension for any serious Virtuemart user.