Items should generally be more useful than currently and should have more in the way of mixed blessings.

Cursed items, for example, should be more than just items you wield and cannot take off. New flags, like a DRAIN_SP and a DRAIN_HP which drain their respective stat and convert it to the other might even be viable wields at some points. Some curses might be active even whilst in the inventory (DRAIN_EXP might be effective in the inventory, for instance). There are tickets already filed for some of those: pval-flipping curse, cannot drop curse.