In the latest episode of The Brainstorm Podcast we discussed using humanoids / monsters as PCs in your campaign.
From my perspective, it can work if the campaign is built upon the concept of humanoids (orcs, goblins and the like) in positions of power, influence and integrated into society. It may be a society in which humanoids are dominant or one in which they are subservient (slaves and / or servants).
Much of this is due to default alignments - demihuman societies are presumed to be neutral to good whereas humanoid alignment is assumed to be evil. Actually, there is a whole 'nother post hidden in the previous sentence.
So, do you allow humanoid PCs in your campaigns? Have you run an all humanoid campaign? Let us know.