Seriously, there are so many important and interesting updates: Shipping and Payment markups, 8 new payment gateway integrations, custom order statuses, integration with Pitney Bowes, "Operate as this user", Back-in-stock notifications, geolocation, product tags and other changes.
A major update of Multivendor: PayPal Adaptive Payments ( send payments directly to providers!), provider commissions, modes of warehouse/vendors as separate shops...
I did my best to describe it all shortly, yet in a comprehensive way in X-Cart blog:
http://blog.x-cart.com/5-2-7-released.html
How do you like it?
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UPDATE 22.10.2015: Release of v 5.2.8
During the testing stage of v.5.2.7 (developer wave) we discovered a critical bug and took decision to release v.5.2.8 with the fix aboard. There are no changes from the functionality point of view. It also
starts from a developer wave, so the upgrade will NOT be available for the production stores before we make sure it's stable for live stores. After that, once the upgrade wave is switched to "Merchants", you will see a notice in the admin backend about the availability of the updates for your store.