These miniature cameras all suffer from a ultra fast shutter which creates the weird prop effects.
I find that swirly line prop-effect particularly annoying. The Sony bullet cam produces an effect like the prop is standing still or slowly turning in either direction which is slightly less annoying, but I've not seen any small camera that can display the prop as a spinning disc or that can change exposure quicker than 2/3 seconds.
Vibration is also an issue. It blurs the image. One needs to make an anti-vibration mount. People doing this seriously use special vibration absorbing bushes like
these to make up a camera mount. They are cheap enough but hard to get in the UK; I have ordered some from the USA.
A cheaper way is to use the highly sophisticated human body mount option, which is the best solution for training since it will give you an idea where you were looking at any given moment. Not popular with some viewers though if you're posting on youtube etc.
I have flown with a bullet cam since passing my PPL and it is quite useful to look back on flights. I did post a couple videos in the personal flying vids section but looking at them now they are pretty boring! In fact it's slightly frightening looking back at how low some of my approaches used to be!