Mircea,

> How do you think about the ideea to develop an application based just on
> buttons and no menus ? Can be those interfaces more understandable because
> of better visibility of all option toghether? Whitch could be the main
> reason for doing all things from menus ?

Buttons take real estate space. It's not clear how much real estate you have left for other things if every menu command is replaced by a button.

Buttons attract attention. Including a button for a seldom used feature may distract the user from the current task.

Too many buttons makes it more difficult for the use to locate the button he needs.

If using a toolbar. Toolbar buttons cannot be tabbed to because they can't receive focus. I would strangle if your application forces me to reach for the plastic rodent every time I want to accomplish a task...

Menu items can be accessed by pressing the appropriate keyboard keys.

Some buttons can help the user focus on the current task,

Whether to include buttons is not always an easy decision. You may want to read some books on software usability to make an informed decision.

Hope this helps,
Daniel