The following has been updated or added for Version 6 and you'll find references in this help file:
Inventory Center - Now has a "Property Grid" that allows you to see important information at a glance.
Accounts Receivable - New AR Batch Payment Center
Accounts Payable - New AP Processing Center (See Overview Accounts Payable)
Payment Processing - EMV payment processing through Vantiv Integrated Payments (formerly Mercury). (See Credit Card Setup)
SMS - Text Marketing allows you to send marketing messages to customer phones. (See Marketing Tools)