It really is a time issue and if you have the time to do it then why not? While a butt does have plenty of fat to stay moist if you brine it you will still notice a big difference so I recommend it. As I said it's really a time issue.
I went ahead and brined it because I had the time and, really, it's easy to do. It was in the brine 12 hours.
The I rubbed it as always and smoked it for 10 hours at 225 to 250. I took it off the smoker, wrapped it in heavy duty foil and then in a towel and put it a cooler to keep.
2 hours later I opened that baby up and it was amazing.
Gave the Direct TV guy working in my neighborhood a sandwich of pulled-pork on a bun w/ homemade coleslaw and just s drizzle of bbq sauce. He came back 30 minutes later wanting to know how I did it and asked me to open a restaurant.
I consider it a success.
For the record, I've smoked five shoulders previously. All came out tender, but this one I almost didn't need to "pull" the pork.
So, to agree completely w/ Martini, if you have the time, brine. I didn't notice an improved taste, but it was as tender as I've ever had while still getting a wonderful bark.