Upgrading items

[penco]

What exactly happens to a rare/unique item when you upgrade it with the cube? Is there a disadvantage sometimes? I am somewhat confused because some strategies say to use certain items un-upped, but it would seem at first that you'd want to upgrade everything.

[kuafu]

When you upgrade an item, the base item changes to the higher version, but the mods on it and the socketed items in it don't change. There're two disadvantages I can think of.
1) Higher requirement (str, dex and level).
2) If an item has enhanced defense, it's base defense is always the max + 1. But the base defense is re-rolled when upp'ed. In rare cases, the re-rolled base defense may actually be lower if you have a very bad roll (e.g.: Arreat's Face).
Edit: also in earlier patches, upp'ing eth items will lose the eth mod. I know it's fixed now, but does that still apply to items found in earlier patches?

[SirDooFuss]

The only downsides are the cost of the runes and the increased requirements. If you up a normal item it's strength and dex requirements increase to that of the exceptional version of the base item. Exceptional to Elite, same thing happens. It's easy to end up with a upgraded item you can't even use because you no longer have enough strength or dex. Often the increase in physical damage or defense is not worth the increase in requirements.

Edit: Pwnd by SECONDS!!!!

[thegiantturtle]

Edit: also in earlier patches, upp'ing eth items will lose the eth mod. I know it's fixed now, but does that still apply to items found in earlier patches?No. It doesn't matter when an eth rare/unique item was found. They will now upgrade properly.