The extreme rarity of items was once a nice idea as it allowed to add meaningful trade to the game . But every modern mmorpg has a central market so basically real player-to-player trade got taken out of the game already anyway. All that's left of it now are completely meaningless inflated prices and the real currency is no longer items but player time. Which I find sad as wasting as much player time as possible is a really poor design target.
I don't say it won't work out for them, but personally I hope they fail with it. Because if it succeeds, then it's obvious that they will next try to figure out how to further improve that income. I would prefer game designers to spend their time thinking about how to improve the game-play instead.
