Do you guys think it will be nice to have a some kind of "full screen mode ? Sort of Firefox F11 button? - when all the menus are gone and all screen is occupied by one (sql, test, pl/sql, command) window?

you mean like "Edit->Full Screen" that exists since version 8 of pl/sql developer ?

cool. Didn't know that.
and can i get ,say , the object browser to reappear if i move the mouse to the location it is ( when not in the full screen mode )?

Yes. Just open a pane (in this case, the object browser), dock it somewhere (left, right, top, bottom) and press the pin button. It should slide to the window border, leaving just a visible tab. If you mode the mouse to the tab, the pane will slide back into the window.

i see. That works when i'm _not_ in the full screen. I guess i didn't say it right:
what i would like to have is an ability to see (for example) object browser to "re-appear" when i'm _in_ the full screen mode. Sorry about confusion.