To add to the other problems I have seen with other users, here are some that continue to plauge me.
Final checkout screen freezes. Clients email me after saying their order never went through.
MIVA blames it on paypal however it happens with every payment form. This has been going on for months with nothing resolved.
Last night all my "Add to cart" buttons disappeared from the website, so now clients don't have to worry about the final screen freezing because they CAN"T ORDER ANYWAY!!!!!!
Inventory has been an ongoing nightmare so I just don't use that feature anymore.
I am now in the market for a shopping cart other than MIVA because it sucks!