Dom said they were still working on eliminating any final latency issues ( Though I don't even think a WMV file is valid way to judge latency ). And like a computer you'll have to face there will be more prep time before it will be ready to use. If you were using a laptop live as a sound source you'd be facing exactly the same thing. Don't expect the Mediastation to be any different, everything is limited by the current state of technology.
As for hitting buttons that is simply a matter having to get your finger onto the correct onscreen item without selecting the wrong item. This depends entirely on the GUI provided by the application being used plus the size of the fonts being used. For live use I'd prefer to use applications that had large well separated buttons to make operations "error free" on stage. Of course it's a personal call whether you want to use a touch screen on stage or not. But in the studio it would be quite workable and a mouse could be used as well if preferred.
The number of button presses is just the same as it would be on using a mouse driven computer ( just more obvious ) and the most important thing is to then be able to save a setup so it can be recalled easily in one operation when it's needed.
[This message has been edited by Nigel (edited 06-30-2006).]