May be quite handy in the Underdark.
As far as I know we do not have torches or the cantrip Light spell in DDO...either would be nice. The advertisement/loading screen does seem to have a player character using Light...
If it turns out that we're not getting either of these, if it can be done without increasing lag, I humbly request that weapons with the 'Incandescent' property act as torches much in the same way that the sceptre does in Rainbow in the Dark.
Here are some of the light sources currently in game off the top of my head:
the torch in Rainbow in the dark
Grease that has been ignited
flammable quest objects such as boxes or furniture
Shadow Walk gives a sort of 'darkvision'
Some fog spells can also help outline objects...
Have I missed any?