is a man of many talents
Bad things happen with the image when keystone correction is applied. It’s enabled for vertical correction on home theatre projectors, to aid in typical projector positioning at the top edge of the image, as this is often unavoidable.We have a BenQ Home Cinema W8000 in lieu of a TV for about four or five years; works really well if you don't need to watch TV in daylight hours. Pull down screen attached to a beam on the ceiling so it all disappears when not in use.
Over the years the fan has started to kick in noisily more often which is a bit annoying - I've replaced the bulb and cleaned out the dust - but other than it's been great. The only feature that would be neat is if it could skew the picture so it can be placed in a corner rather than straight on.
Enabling both horizontal and vertical is typically only found on super portable presentation projectors.
High end projectors feature lens shift, where the lens is physically moved in relation to the light engine in both vertical and horizontal planes to achieve better projector positioning and avoiding the need for digital image manipulation to correct for keystone.