Cursed items are the bane of players alike. But that does not mean that they cant be more fun then a curse.Their is a big problem when a player knows when they have a cursed item and their character do not. How do you get passed this? Here are some ways around this.
Make the item effects slowly appear. Say, a player has a item that will turn him or her into a goblin.Have the effects be the humorous side of being a goblin. Bad manors,start to smell real bad,a spot in his or her private area turn green( try and explain to the party cleric about this one!) and so on.
Do not hint to the player he just picked up a -1 longsword,for the first time when he swings the sword and his role is one less instead of one greater,the player will know. Have the effect of the -1 happen after 2-7 days later.The player will not know what he might have picked up that is giving him a -1.
Just remember that you are out to tell a story and make your players have a good time,not out to make their life miserable.