Dan, I'm not sure I understand your scenario 100% - how would you verify the credentials of the primary user? For security, we require the user to first log on and also have full access rights to the other mailbox they access.
Paul, it's true we don't have this view and neither does Outlook. We have had many requests for this and even more the month view. Know that we do have these Calendar features on our own wish list.
Pierre, we don't support adding images in the signature this time but thanks for the feature request - we'll add this to our list as well.
John, I think you'll be happy with our new mailbox quotas feature. Hovering over the top Mailbox folder will allow you to see current space used vs. total space allowed. Once the user is over their warning quota the quota information is shown as an infobar over the folder list. Look for a more in depth post on this feature soon...