IIRC the issue with AWT and non-reparenting WMs is mostly limited to popup (ie. override-redirect) windows that are positioned in relation to some kind of owner window (which means menus, tooltip popups...). AWT simply expectes that parent window of its window to be the frame window of reparenting WM and calulates the position in respect to that, if there isn't the frame window the position of the popup inside root window will be calculated as if the root window was the frame, which can result in anything from the position being slightly wrong (eg. shifted down by the height of awesome's "menu" bar) to the window being completely off-screen.