Whats an Example of a Good Viewing Angle for a LCD?
Looking directly at a monitor head-on is 0 degrees
Attempting to look at it side on (you can't see the screen at all at that point) is 90 degrees.
A viwing angle spec of 130 degrees means that you get reasonable performance from 65 degrees in one direction, all the way to 65 degrees in the other direction. 170 degrees means 85 to 85.
It's difficult to explain viewing angles without seeing it for yourself. But if we take a 130 degree rated monitor and you are looking at it head on from a distance of 2 feet, you could continue to see the image if you moved sideways up to 4 feet.
For most people 130-140 degrees is sufficient. However, if multiple people need to be able to see the screen at one time, then a larger viewing angle can be important.
The other thing is that viewing angle is not a sharp cut-off: colours gradually degrade as you move away from 0 degrees - the 'viewing angle' is just the point where the image gets unacceptable. If you are doing design work, and accurate colour/contrast is required then a larger viewing angle may be important.