How do blessed items work?

[RndmNumGenerator]

Everyone knows it; blessed is better. Except for a few rare cases, you will almost always want to bless your equipment. The question is, how good is it? If you don't have the means to bless an item(usually in the early game, though it sometimes happens later) is it better to use, say, the Blessed +0, 1d6+2 weapon, or the Uncursed +3, 1d6+2 weapon?

[prime]

Blessed weapons 1.5x damage to undead and demons. I believe that's the only difference as far as damage goes.

[Twinge]

In addition, blessed weapons are less likely to get destroyed via traps and the like. But early game, easily go for the uncursed better ToHit/Damage weapon.

[Silfir]

Except if you find demons or undead. Switching weapons is easy.