The most recent feature tempest in a teacup is around message recall in the upcoming Notes and Domino 8 release. Ed and Mary Beth, brave souls that they are, solicited feedback from the community. Through the ensuing discussion many people suggested that Notes 8 mimic Outlook 2003 as its default, just for the sake of user consistency.
That's honestly not possible because of inherent differences in how Notes and Outlook function. First, Outlook message recall is processed on the client rather than the server. Second, the amount of useful control administrators have over Outlook is a number approaching 0. Let's examine why these are relevant to message recall.
Message recall notices in Outlook are processed on the client, which means they are received into the message delivery folder. This poses two problems: first, if someone is on vacation or out for some other reason, the request won't be processed until they log into Outlook again. Second, and more importantly, Outlook users can configure their mail to be delivered to a personal folder. If the user has his mail delivered to a personal folder the message recall will never work. The person sending the recall request will get a failure notice and the original recipient won't even know the recall request happened. Finally, and to the second key difference listed above, as an administrator you can't force the mail delivery folder to be something you can control.
The lack of administrator control over Outlook is a huge problem. You have to use the Office Administration Kit to deploy custom installations, then use Group Policy Objects to further refine settings. Many options aren't even available to be set, and there is no ability to prevent a user from changing something that is set via policy.
As it relates to message recall, an Outlook user can select to not process recall requests automatically. If a user does this (and most do), there is no way for a recalled message to be automatically deleted -- even if the recipient has not read it yet. The recipient will get a request in his inbox and can choose to allow it or not, at his discretion. Administrators cannot prevent the user from making this change, either.
By contrast, Domino will process the mail recall on the server. There is no requirement that users log into their mail to make anything happen. Furthermore you can configure Domino so that it will always delete the message even if is has been read. Domino offers robust and granular server-driven control over what a user can do with the Notes client, so you can not only set the property for the user through a policy, you can prevent the user from changing it.
Nathan's writeup about how message recall "should" work is very good, and it sounds like something that would be worth implementing in the OpenNTF Mail Experience template. E.g. click recall and it presents a list of only the people in your current Notes domain. I'm not sure how much further it can be taken without adding in some server-side pieces to store metadata (does user allow recall, etc.). If there is enough interest and someone is willing to help me spec out all the possible pitfalls, I'm willing to code it. Any takers?