The inventory feature is a good addition, preventing the often pointless waste of rewards.
I do think the cost reduction certainly an advantage that major gold users will utilize extensively. Although it will most likely be profitable for Innogames, the trend of continually introducing premium advantages will eventually motivate players like myself who use minimal gold to leave grepo altogether. I understand and accept the profit motive with the game, but I would suggest that while more premium features get introduced into the game, it might also be reasonable to make one of the five premiums, like the administrator for instance, part of the basic free package. Otherwise I think the trend over time will be for players like myself to finish the world they are currently playing and not move to a new world. Eventually the participants will dwindle, and so will the profits.