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I just tried time freeze and rendering is slow and the video doesn't play after rendering. At least it doesn't crash but not very useful at all. I'm on iOS 7 iPhone 5.

If this is the best the AppStore has to offer, then to answer you question, I think we do need slo-mo.
 
Time freeze works ok here. Interface isn't as good as others. The others are good for some loose change. Pretty fun until most if us non s owners upgrade to the iphone 6.
 
added this one to my list at the top. It's definitely my favourite!

SlowCAm this has a cool 'tap for slow motion' feature
 
You should add TruSloMo to the list. It's an app I made. It converts slo-mo videos shot with the stock Camera app so that they can be used by other apps like Instagram and iMovie.
 
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