The extra gamut, stability and longevity. It seems there are only advantages (except perhaps price).
we don't know yet! From the specs the LG is a great display. As to the LED backlight, yes, the NEC 21'' SV Reference (AFAIK the first LED display a few years ago) is a great display ... but it is a highend display.
I'd take a look at the calibration software. Actually it's good to take the manufacturers calibration software when using colorimters (instead of spectrometers) as the manufacturers implement correction curves for the specific display/measurment device (at least Quato and Eizo do so and it works just great).
The calibration software should be capable to adjust luminance, different TRCs ("Gamma"), white point (so far nothing special) and in addition you should be able to set the black point and to adjust the white point manually (but triggered by the software).
Do you know of a specific thread about this?
not a specific thread just some scattered comments in a German prepress forum.
Variation in a series should not be a big problem if the dealer/manufacturer is okay - if you get a bad copy you just send it back.
I sent back 2 Eizos and took the third... a bit shipping trouble but nothing serious.