Well the tv does have limits - to avoid ruining scenes there is a limit to the distance the tv will interpolate between, so if the fps is too low then the tv may as well be the same speed as the fps as it can't add in the extra detail as the "jumping" of the objects may be intentional. I only notice it when something is moving smoothly - an actor turning their head or a tennis ball is a good example of this. Also due to the higher framerate the "ghosting" which can happen on screens is gone as it may need 3 or 4 refreshes to completely remove the previous position of the object completely so on 100hz this happens a lot faster than on 60, helping reduce blurryness as well.
You won't notice the difference if it only showed 1 frame - you can only see the difference on things which are moving a relatively small distance across the screen between frames - if it was a 15fps source then the tv couldn't calculate the distance between:
f---------------------
and
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properly as there is too much unknown detail there for the tv to be able to calculate - the scene will have changed too much with too much unknown data for the tv to accurately calculate what should go where, so it does have its limits.
As i said in my original post my opinion on 100hz is that it is nice, but it is not a "killer feature" and so other factors such as screen clarity, contrast ratio (to a limit), colour reproduction and sticking within your budget must all come first, if you can meet all of those and get the choice between 100hz and 60hz within your budget then go for the 100hz as you will get some benefit from it, but you won't miss it if you can't get it as you can't notice it not being there (if that makes sense).
Really if you want to see if you think it is worth it go to a brick and mortar store and look at 2 screens next to each other (one 100hz, 1 60hz) with the same source and see if you notice any difference - these things are always down to personal preference at the end of the day as some people will say it's very important while others wont notice the difference.
**edit**
as for the complexity the tv is looking at 2 bitmaps, quickly scanning for similar patterns very close to each other in the bitmaps and creating intermediary bitmaps to display - with dedicated silicon designed around the problem it isn't too complex, but as i said it does have limits and a lot of the bonus in sports especially is the reduction in ghosting as the more refreshes per second the faster the previous image's ghosting is removed, reducing blurryness). This is of course how i understand the technology to work, i could be mistaken.