I can see gradient step on my HP 2335 (1920x1200) IPS display Monitor (with an LG display panel that was similar to what was used in Apple Cinema Displays of the time). Just giving verbosity of the monitor details for reference. Interesting read though and I found it surprising that even 24bit color can have issues like this. Possible that some high res IPS displays since mine have eliminated the issue (since the 2335 is 4-5 years old now). Wish my 2475 wasn't dead or I would test against that as well. I don't really consider either of these a good comparison, but I don't see it on my Nexus 7 or my Galaxy Nexus (though that's a Pentile AMOLED screen).
Some that cannot see it might have missed the author's advice at the bottom:
I received some great feedback from readers. Most importantly, it was pointed out that some low-cost LCD monitors down-sample to an even worse color depth such as 18-bit or lower. In fact, some readers were not able to see the difference in the colors above precisely because their monitor removed the difference by down-sampling.
The problem with some AMOLED screens is that the different colours efficiency decays at different rates. Which is why early versions of the galaxy(or similar samsung phone) always has that horrid blue-green tint to it.
Another problem is ambient light. if you're wearing a red tshirt, and there is a source of light other than your monitor its going to throw out the colour balance.
There's actually methods being worked on to compensate for color degradation in AMOLED over time[1]. Many of the AMOLEDs being used by Samsung are also Pentile (since they're cheaper to produce), which is even more likely to suffer from what you mentioned as well. Originally, phones like the Galaxy S and S2 did not have a Pentile screen, but starting with the Galaxy Nexus, I think they all have since (including the S3 and the S4, albeit higher quality ones).
Some that cannot see it might have missed the author's advice at the bottom:
I received some great feedback from readers. Most importantly, it was pointed out that some low-cost LCD monitors down-sample to an even worse color depth such as 18-bit or lower. In fact, some readers were not able to see the difference in the colors above precisely because their monitor removed the difference by down-sampling.