Like many other users I have been unable to install the latest WhatsApp XAP from marketplace, even after restarting my phone.
For those who did manage to install it, WindowsPhoneApps.es reports that the app appears to invoke the Background Audio task, which takes users directly back to the app when tapped. As a likely side-effect this the app does not have to log back in again when resuming from being tombstoned, but this is probably a misuse of the API however.
In our comments users are reporting numerous bugs with the update, such as repeated freezing when chatting.
Have our readers had any of these issues? Let us know below.