Is it a proven fact that the newer LED displays are accurate enough for photographers? I know that there are some strong arguments for using them (no warm up time, longer lifespan, less power consumption). But, with that said, is the technology a proven itself yet? Should I steer away from purchasing the older LCD technology (like the NEC 2690, or 3090)
That's a very good question, and I must admit that I haven't read any definitive answer to this question.
Theoretically speaking, high power LEDs are more stable than CFLs, in addition to having a longer life-span (can be more than 40,000 hours, as compared to typically around 10,000-15,000 hours for CFL), but no matter the lighting source, production quality control is important.
If there is uneccesarily high heat build-up in a LED array, lifetime degrades significantly. If humidity penetrates the diode, lifetime degrades significantly. If the LED isn't protected against UV light, lifetime may degrade dramatically if exposed to UV-rich light.
For LCD panel backlighting, UV shouldn't be a problem, and humidity is a factor in the manufacturing process. Cooling is a factor in system design.
So, again theoretically speaking, you can avoid these problems.
When it comes to controlling intensity accurately, yes, diodes can be controlled nicely, given decent controller circuits.
Are we there yet?
Let's see how e.g. Apple's new 24" panels turn out in a couple of years; there are only slightly less than 9,000 hours a year anyway.