I just did it yesterday. Turned out great! It took about 11 hours to get it to 200 degrees. Let it rest an hour and it pulled fine. I was surprised at how much meat was there. I will have plenty of leftovers.
I will do more picnic shoulders after this experience. I think I paid 99 cent a pound for a 12 pounder. They were outta butts and I'm kinda glad as I don't know that I would have tried it, otherwise.