I had a great experience with Cart2Cart. Reading some of the negative reviews here says more about how complex ecommerce migration is than anything else. I will say that I highly recommend paying the extra $ for their assisted service, which I did. It is totally work the extra $200 or $300 because you get a project manager who is very available, and you get to tweak your migration settings to make sure everything is just right. With the automated tools they offer, you're on your own. But their customer support on my project was fast and responsive to my questions, and they were able to make any adjustments I needed. I migrated from Virtuemart to Shopify with over 12,000 orders and 4,000 customers. The migration was smooth. They scheduled the last "new data" import for me at a time I chose (within their working hours). And the migration was a success.