For the bad part --
Proof of stake is not good.
It encourages holding the coins as investment, avoiding it's circulation, i.e. true use as a cryptocurrency. Then worst -- PoS looks at the coin age; the longer you're holding a large amount of cryptocurrency, the higher the chance of mining a block, which further reduces chance of circulation. However if the profits proof of stake is giving you is negligible, then we may nullify this disadvantage.
You may simply transfer coins from one address to another to maintain 20% interest rate.
20% is HUGE... it's too much and that gives a bigger inflation.
