Do you guys think that Apple deliberately introduced the yellowing issue into the screens to force users to upgrade to the 17" Macbook Pro?
No.
How is it possible that screens from 3 manufacturers can exhibit the same issue?
Dunno, but it should have been sorted out a long time ago. The fact that different manufacturer's screens have similar issues perhaps implies that the technology is not sufficiently mature yet, or maybe that the investment in quality control to significantly reduce the problem is more expensive than just replacing the few screens that get returned - at least while they get through the numbers of displays already manufactured with the problem.
The other reason of course might be nothing to do with the actual screens themselves, but more on the MBP side - some controller/shileding/power supply/graphics card issue - this would explain why the issue occurs across different manufacturer's screens.
And I'm sure that there are plenty of people with defective screens who don't really notice - after all, this issue is best seen under certain conditions, and may not be noticed under "normal" conditions. The fact that I pulled out three machines today and they all had the issue, implies to me that any MBP's of at least the same spec sold from that store today would probably also have the issue - but I'm guessing it's unlikely that any of those will come back.
I wonder how many of these bloomin' things I'm going to get through before I get a "good" one? My count is three so far, and I'll go to a different Apple Store on Monday (probably the London one) and go through the whole process again.
A display that displays white properly in the top half, but then fades down to display it as grey (slight yellow ting) in the bottom half is not what I can "within spec". I want/need a machine, so I have to keep playing the lottery until I don't lose.
What's more surprising is that the Macbook Air, which has a similar spec screen, doesn't appear to suffer from the same issue - are they using a different screen manufacturer for these? A higher spec / more expensive screen?