Global Requirements
Consistency in user interfaces lets users make less errors and they feel more secure in what they do.
In theory all clients should conform to the following requirements. In practice mileage depends on what the client technology gives.
Accessibility
If a client technology provides means to make the interface more accessible, they should be followed.
Design Patterns
Operating systems have design patterns that describe how things should look and how standard processes should work. If we develop a client for a system that provides such a catalog we should follow it. Users will honour the consistency, feel at home and will make less errors.
information architecture
navigation structure
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messages and notifications
We should provide a set of MM3 specific help messages and notifications. Any client should use these, so users get a consistent experience - no matter which client.
If where you write, "Main menu options will be ordered by usage frequency" you mean dynamic reorganization, I am concerned. I have found Microsoft's and Adobe's efforts to "streamline" their menus by hiding things that haven't been used recently and moving items to the top just after I get used to finding them elsewhere around to slow me down more often than it helps.
Adding a short "frequent tasks" list -- sort of like recently used files in Office would be useful, but I would suggest that it should be distinct from the main navigation structure. There is a real risk that dynamic reorganization will actually hinder users by frustrating them when features they're still learning move around. Dynamic menus definitely do not make me feel more secure in what I do.
(Unimportant: Is there a special meaning for "wizzard" with two "z"s instead of the usual one? I tried Googling and found a couple references to musicians...)