Going back to Gene's original point about the effectiveness of reflected sound from the top-firing drivers, it seems whether the drivers are angled or not is sort of splitting hairs. Speaking without the benefit of an accoustical engineering background, it seems the sound from the driver will have a pretty wide dispersion angle, only a fraction will hit the ceiling at the optimum angle, and only a fraction of that will be reflected to your ear. That means no matter what the angle of the driver, the reflections will hit your ear from a host of different angles, and with a host of different timings and amplitudes, all of which will be exacerbated by the position of the speaker, chair, and height/shape of the ceiling.
My pedestrian reasoning says all this will work against the intended effect. Not to say there will be no effect, and only listening will reveal the desirability for each person. I'm just not so sure how much difference the angle will really make.