You can upgrade items with bonuses by paying the difference between the two. Thus items like cloak of resistance are similar to bonuses of a weapon or armor.
Charberus said:I don't think that any property should go on any item (like boots of natural armor, headband of dex). That stuff just doesn't seem right. There still should be a limit to what properties items should have. Wotc has posted on this stuff before and gone into alot of good details as to why certain items have certain properties.
Magical Items have a chance of being flawed. The chance isn't great, but it is still there. Only I know the chance of this occurring. [Flaws are not necessarily bad; mainly, it adds a little extra interest to an item and makes some of them a little more unique.]