Brackets allow tilt adjustment, not height adjustment, but the point is that you can have your telly high up and tilted down a bit, or lower down and not tilted down so much, i.e. the availability of tilt adjustment means that the height isn't critical.

The thing you're wanting to avoid, at least for LCD TV, is looking at a TV from below its centre-line. Lots of LCDs have a good viewing angle left, right, and up of centre, but not down.

Peter