Image retention does still occur, regardless of what some people may say. Even with the sets that are allegedly immune to it - leave a white square on screen for more than thirty seconds, and it WILL be retentive when the screen goes to black or grey. However, it will be washed away by moving images, almost as quickly as it appears. This is why most people never see it, but it does happen. Cast iron fact.
If you take the white box example to the extreme, things like game HUDs and white text such as "best time" in racing games, will absolutely cause some sticky image retention. Again, many people may never see it before it gets washed away. If you're especially brutal with the set, and leave static images onscreen for several hours, they will become borderline burnt, and will take several days to completely clean away. Again, even at this stage, it may not be noticed, depending on the content being viewed after the event. This is really the only time that you need to use scrolling bars as an aid. Normal mild retention will be washed away before it's even noticed, usually.
Yes I bought a 2013 Samsung LCD. Very very good. Best blacks I've seen from LCD, but terrible viewing angles. Also the backlighting was still cloudy. Not acceptable for me when paying c.£2300. I replaced it with a VT65 plasma, and whilst it's not perfect, it's far better than anything else I've seen. I'm speaking from the perspective of someone very much into home theatre though. Other people have different priorities. I know someone with the aforementioned Samsung, and they're more than happy with it. And rightly so, as in their viewing environment it looks great.
As an aside, in my opinion the whole motion argument is misunderstood. Modern LCDs use use a lot of frame interpolation to mitigate image blurring. Plasmas also have this in order to increase the frame rate of 24hz, but in my experience a properly setup plasma actually looks a bit jerky compared to LCDs. The problem is that frame interpolation causes artefacts and even visible frame skipping. In my experience so far, it's easier to obtain a balance between blur and artefacts with an LCD, than it is to obtain a balance between jerkiness and artefacts with a plasma. Once you get used to the somewhat filmic look of an unmolested plasma panel, it seems way more natural. All IMO only of course. Different people have different ideas about what constitutes good motion handling. Generally, a plasma (with frame creation off) produces a more realistic look.
Sorry for rambling
