Current version of Dooble (1.47) places too many menu under menubar (10 menus compared to 7 menus in Firefox). This menu make the interface looks complicated for the first usage. The placement of "Settings" option also not common for an application. Usually "Settings" option are under "Edit" or "Tools" menu.
The size of "Settings" window are also too big (around 1024x600) which really not comfortable when user using small screen resolution computer. It can be set to become smaller but will make the window a bit messy with scroll bar (usually "Settings" window aren't using scroll bar.
My conclusion is the placement of menus and options should become a concern as comfort and familiarity is something that user may judge for the first impression. (See also my review in Sourceforge)