I am working on an update to ListMail and I can say some AJAX is being used in the interface. As for -every- page being AJAX-driven, ie: -never ever reloading the page at all-, I know I could do it but I am not sure that it will be the case. I think such an implementation could get overly complicated with limited benefit. I've had some success simplifying AJAX so there will still be extensive use of it, however.
Regards