The stability of Magento as a company and product is still in question. In 2011, Ebay had acquired Magento and has been using its staff to create X.Commerce - a platform that will rival Magento itself. In my opinion this could mean that the stability behind the company is dwindling and a new direction will be taken.
Slow unless you have a dedicated line and server.
Cumbersome to update
Robust Community that may or may not lead to X.Commerce
Templating system seems like it could be limiting
No Gift Certificates
Multiple Shipping Points
Cart Always Displayed
Product Import from Excel Sheet
Who will do fullfillment?
Multiple shipping locations?
Multiple locations to ship to?