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:
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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.