The first thing that comes to mind when I read this question is, where are you able to purchase either v8 or v9? Right now, Intuit is only selling v10. If you are planning on buying an old version off of a site such as Ebay - please be very careful. Make sure it is an unused/unregistered copy. Sometimes people sell licenses that are already registered and it could cause you some major headache.
With that said, v9 came out with these enhancements:
Quick Add Item from Document – Quickly add a new item to inventory and immediately process it without leaving your current document.
Sales and Customer Service
Track Business Customers – Allows you to record customer purchase order numbers on sales receipts and customer orders and then, if integrated with QuickBooks financial software, the PO # is automatically carried to receipts and invoices created in QuickBooks. Also, displays the company name throughout Point of Sale and allows searching and filtering of customer list, receipts, and reports by company name and customer PO numbers.
Customer Features Added to receipt Simple View – Now, you can list a customer on the Simple View receipt. and basic customer-features, such as customer discounts, special tax handling, loyalty rewards, and charge accounts associated with the customer are available.
Customer Center – Provides one-click access to customer communication options, a list of summary statistics for your customers, and answers to frequently asked questions.
Discount and Coupon Enhancements – .Discount options, including a new coupon option, have been consolidated in Price Manager.
E-mail Marketing Lists – Create targeted customer lists, based on sales history or customer record information. to send to a third-party e-mail marketing partner.
Discount Report Enhancements – Discount Summary and Cash Drawer reports have been improved to include breakouts of all discount types.