Updated with comparison pictures of what AMA low mode does to improve the monitor (Based on XL2720Z V3-V5 firmware. XL2420Z, XL2430T, XL2411Z will have improvements, but much less (basically, minor improvements rather than major improvements). V2 will make the AMA twice as bad so V2 cannot be used.
Blur reduction on, AMA high, default (This was taken at 120hz, strobe duty 009, contrast 43 (1.5ms persistence with VT tweak) with strobe phase at 000.
Blur reduction on, AMA low, contrast 43 (don't remember the refresh rate but it is irrelevant--this is how it looks).
You can VISIBLY see the difference massively. All inverse ghosting has bee reduced to the point of normal ghosting. While this is a 'big' swing in the opposite way from a perfect calibration, sometimes on 2D side scrolling games it helps. Sometimes the minor XL2420Z/XL2411Z boost is better. You can improve this on the XL2720Z even more by dropping contrast from 43 to 10.
120hz, AMA low, contrast 10, Strobe duty 009, camera exposure time -2.0 to make moving images clearer (that's why the screen is so dark, NOT the contrast 10, although lowering contrast does make things more washed out and has an effect on brightness in a way, but not on the backlight directly).
The BENEFIT of the XL2720Z "overshooting" the AMA low so much is a HUGE benefit to blur reduction OFF, by using the bug in the first post with profile switching. This is because, blur reduction off's AMA high is basically the same as blur reduction on's AMA premium! So the 'AMA low" is shifted heavily towards the right if you do this, making blur reduction off's AMA not show hardly ANY ghosting whatsoever--ZERO inverse ghosting and barely zero normal ghosting!
The XL2420Z, XL2411Z, 30T etc would all show inverse ghosting, but obviously less, but not much less.
Here is 100hz:
100hz, blur reduction OFF, AMA high.
100hz, blur reduction OFF, AMA low, by switching to a preset (gamer 1/2/3) that has blur reduction off, after doing AMA low with blur reduction on.
Pics speak for themselves.