We recently upgraded to 1.3.9 from 1.3.8 and experienced the double PayPal entry issue with using Website Payments Standard (http://www.zen-cart.com/forum/showthread.php?t=169037). We switched to Express only to have a customer unable to checkout because she was trying to ship to her boyfriend's address, and of course, this was causing his address to be sent to PayPal as her billing information, and Express does not provide a way to modify that information. I did as suggested and contacted PayPal MTS with a feature request. Here was the response:
"Unfortunately, this is intended functionality. PayPal does not intend to change this as the entire purpose of Express Checkout and Website Payments Standard is to allow buyers the confidence of entering their payment and billing information on a secure PayPal hosted checkout page.
Website Payments Pro (WPP) allows you to collect and send billing information to PayPal, but this is because WPP is hosted entirely on your website.
We appreciate your feedback and apologize for any inconvenience this may cause,
Russell
MTS"
This is, of course, very frustrating. Our company sells music equipment and sheet music and many of our customers are teachers, students, or parents of students and have one billing address and another shipping address (often a school or dorm). We feel like we have to choose the least problematic issue - either continue to use to Website Payments Standard with the known duplicate entry issue and explain to many of our customers that they weren't charged twice, or go with Express and lose customers who require separate billing and shipping.