I urge you all to watch what is happening with vericoin before moving to PoS.

over the weekend mintpal was hacked 30% of vericoins  (8M) were stolen.
the devs fearing 51% rolled back their blockchain in order to stop the theft.

this has created a huge controversy which can be seen in full detail on the vericoin thread (and the various a news articles)

they did this because if a thief gains 51% of a PoS coin they can have majority control of the coin forever because they can stake and very easily keep creating new coins.

this is not the same thing as a 51% PoW attack that only gives the attacker limited control while they hold 51% of the mining power which in a healthy coin ecosystem is continually growing and supported by new miners.

PoS encourages hoarding and centralization of power more so than PoW...
the effects are amplified the smaller the coin.

I expect in the future we will see more PoS coins suffer from this vulnerability