I can't currently open "secure files" without storing them first. Would like to have 1Password 4 Windows handle that automagically.
If it needs to create a temp file somewhere, it should also delete it quite soon.
I think that depends. First of all I am only a user too and not involved with 1Password.
If 1Password prompts you where it should save the secure file than you as a user can choose a safe place (e.g. a mounted TrueCrypt volume). Therefore you have more control where that sensitive will be saved. It is also in your control to delete it after using it. With that power comes also the responsibility to choose a secure place and delete it securely afterwards.
If 1Passwords is going to handle that as well for the user than I would expect that it will create a secure place to safe (not in the current file system) and it also has to securely wipe it afterwards. A normal deletion with moving the file to the trashbin is not safe at all.
@lcorneliussen, that's exactly the logic behind our design decision.