Windlings uses poisons to help them bring down beast and bad guys much larger than them but they rarely use deadly poisons. They mostly use Keesra (sleep) and Whadhyra (paralyzing).
They speak about that more in the Denizens, including description of the poisons.
I can see the use of poisons as useful in some situation, especially to be used on original ways. But I'm not much in favor as a 'permanent' tool on PC's weapons (i.e. a pc constantly keeping their swords coated in poison) it just add a layer of complexity with no real advantages (i.e. if you 'force' the GM intro keeping track of poison for the PC, then you can be sure the bad guys will also have poisons too and nullify the 'advantage').