I had used Cart2Cart 3 years ago for a migration from OSCommerce to Joomla/Virtuemart. I struggled with Virtuemart for 3 years and am sick of it. So remembering the good job they did 3 years ago, I had them migrate my data from VirtueMart to WooCommerce. Everything went smoothly except my photos didn't get transfered correctly.
I emailed them and gave them FTP access and they got everything fixed right up. I think they went out of their way to get my stuff up and going.
I will use them again when I get sick of WooCommerce unless it works like it is supposed to.