I have just joined the shoulder seams on the Badminton sweater. A recent post on the Fiona's Knitting blog mentioned Russian grafting and recommended it for an unobtrusive join (she used it on double moss stitch). I had not heard of it, but she has an earlier post that gives very clear directions.
I don't think I have achieved quite as neat a result as she did, but I'm pleased with my effort. It is a very flat seam, and I think is about as unobtrusive as I could hope for, especially on the neckband. Since the original pattern avoided shoulder seams altogether, it would be a pity if my modifications made the shoulder joins very obvious and lumpy.
Just shows that reading other people's blogs can be really useful.