This is one of the upgrades to your i30N that really gives you results and is not just waste of money.
Engine movement is reduced so you gain better feel for shifting gears, reduced wheel hopping, power delivery is faster and smoother due not rocking the engine as much as oem bushes.
Downsides…
well you need to spent few euros to buy it…
You need take half an hour to install it.
That is it.