I can only speak for versions 188.8.131.52 and 184.108.40.206 because those are the only ones I've tried this with, but I suspect this issue appears in other versions also.
Several things I've noticed when using PayPal Express Checkout:
Transferring shipping options does not always work, and the call-back always takes a really long time.
A user clicks to checkout with PayPal, they arrive at PayPal's site and the shipping options (when they work) take a while to load. Sometimes they don't load at all -- nor does the indicator even suggest that a call-back is requesting the shipping options.
When the options do load this approach can result in a successful order, but it's hit-or-miss.
Not transferring shipping options re-routes the user back to a strange/broken order review screen in Magento. The header of the site is rendered twice. There is an option to select shipping, but once that's done the page redraws with another selector to select the shipping option again. It's just broken.
This approach can never result in a successful order being placed.
If a PayPal order ever is placed, the "Last 5 Orders" box on the Dashboard does not display any customer information -- it's just a blank row.
Also, in the order details, the comment history has an entry with what appears to be bad data:
Authorized amount of $50.00. Transaction ID: '<a target="_blank" href="https://www.paypal.com/cgi-bin/webscr?cmd=_view-a-trans&id=29348328IJD9302">29348328IJD9302</a>".
Why is the "Transaction ID" displaying HTML -- shouldn't this just be the value?
I'm less concerned with #3, but does anyone know what's going on and if there is a way to resolve #1 or #2?