It's funny that you claim it is common on H-IPS panels, because we have over 30 Dell U3011 in my research lab and they are all H-IPS displays and show no image retention, even when left displaying a static image for days at a time. I have never seen any LCD panel (IPS or otherwise) that exhibits image retention until now, and I've spent intimate time (read: weeks) with over 100 different panels.
It is clearly possible to create a panel which reduces this undesirable characteristic to be undetectable to the human eye and yet you seem to think it is "noticeable" on (what I can only assume to be) most if not all IPS displays?
I think Displaymate (a company that specializes in testing display panels) has more credibility than some OEMs which doesn't even manufacture its own panels and maybe just propagating the original rumor.
Source:
http://www.displaymate.com/news.htm
I have two NEC 2490wuxis - fairly high end monitors, especially when they were new. They do exhibit some IR. Doing some research, almost everyone with those monitors sees some IR. I had a 24" iMac at work that exhibited IR (though admittedly this particular was bad enough that I would have returned it if it were mine).
The only IPS displays I have that don't exhibit any are my NEC 20WMGX2 LCDs. And those are gaming LCDs with AS-IPS displays, so I'd imagine they were designed to refresh a bit quicker.
And I would trust two computer manufacturers that do employee actual engineers over some guy on macrumors who's on a crusade against LG.
If you want some physics behind why image persistence occurs, read through
this. Note that this article predates H-IPS displays. I do believe S-IPS were less susceptible to IR than other LCD technologies. But my experience with H-IPS (my own displays and several others) has been different.
That paper focuses more on "Super TN" panels, but the principles can apply to IPS displays. The implication is that minor changes in pixel structure can have a fairly dramatic impact on ion movement and can lead to IR or other artifacts. And since IPS LCDs have some asymmetric current, you can be sure that you're going to have some an uneven distribution of ions. H-IPS (and similar technologies like e-IPS and AH-IPS) have a fairly different electrode structure compared to previous iterations of IPS - IR/IP/ghosting very well could have been one of those unforseen consequences.
You may not have seen IR on your LCDs until now, but you probably weren't looking for it either since it's generally not hyped up like any issue with Apple products. Under normal operating conditions, I still don't notice any IR on my display. Yeah it's noticeable if I load a checkerboard pattern for 20ish minutes and then immediately switch to a gray screen... but that's not what I'd consider normal use. And even that clears up within seconds.
Any other static image (such as the OSX dock) has not actually "ghosted" on my display, and others seem to indicate the same. I've left my display on overnight, and there still wasn't anything really noticeable.
One factor that does effect the image retention is heat. If your research lab is anything like mine, then it's probably pretty cold in there. So IR is already less likely. There are complaints of IR on the U3011 (and pretty much all other IPS LCDs) if you look around.
