I couldn't find the poll, but I have tried GTS Negotiationa bunch of times now. It's rather fun. :D I've found several people with shinies, but as soon as they realize I have nothing for them, they leave. XD
I have gotten some valuable things out of it, though. I got all Isshu starters, a Piplup, a Turtwig, a Zorua, (YES) a couple of version exclusives, a Wynaut, a Shuppet, a Slowking, and a Lapras. :D
I'd still take one, I would use it on GTS like you said. Croagunk code? Wonder what that unlocks you... (A Croagunk maybe? XD)