Hi redleaf!
I don’t know exactly how do you understand the sense of "banding". Basically you should recognize for example all 128 stripes at the same width if 128 levels of digital signal from DVI output are produced by testing application.
(only 32, 64, 128, 256 levels of test-patterns are recommended - don’t use other count of levels for serious testing)
If you see some fusion of 2 or more stripes into one only, thats the "banding" in original sense of word. Dependend on ambient light conditions and relationship to brightness of display its usually not easy to recognize the differencies in the lowest levels of darkness. You can try to change the "hardness" of gradation with Gamma tool in Color-menu to lower level to make differencies of deepest tones more visible.
Then we can control a "neutrality" rendering with the greyscale-stripes pattern. If you see some drifts of general tint of greyscale pattern (all R-G-B channels are the same value at every pixel) then you can say the neutrality isn’t perfect.
And what is expected after all?
Do you mean the 500EUR-LCD presented as office display for safety reproduction of images is the right tool for photo retouching with professional requirements? No. EIZO CG-tool is the right conclusion for photo-manipulation.
Models with 14 or 16-bit signal processing are perceptible better in rendering of neutral tones or display uniformity (due the DUE).
I don’t believe you can find any other 20" widescreen LCD in 500EUR-class better equiped for photo-editing... maybe I’m wrong.
Have a nice time