Many coins have took risks with PoS by now, and no major problem have been found.
Dogecoin's developper consider that using PoS might be a good idea no sooner than the 600000th block, so that's plenty of time for other coins to thoroughly test it really.
Is he considering switching to PoS exclusively?
Or having two independant algos: one block goes to PoW miners, another goes to PoS holders?