My usual blogging timeliness here. News broke several weeks ago that the Foxp2 gene, one that is nearly identical in all mammals except humans and is associated with language problems when it's defective, had been experimentally altered in mice to partially resemble the human gene. They found the mice vocalized differently, behaved differently, and had more developed neurons in the parts of the brain controlling fine motor activity necessary for vocalizing.
So I think it would be very interesting to see how the same change would work on chimps. Those who think that chimps are on the far side of some ethical line that separates humans from everything else shouldn't really see any problem with this idea. I would hesitate and think a long time before genetically altering chimps to make them smarter, but the main change from this gene, probably, might just make it easier for chimps to verbalize what they can already do by sign language (or maybe it would do nothing that substantial, who knows). I think that change, if it happened, would strongly affect us and how we deal with great apes if all of us could hear them talk.