I've got one. I like it. I usually use the sharpmaker, but the Double stuff works well in a pinch. I also have the extra fine bench stone, which I havn't even used yet. The other double stones that I considered were the DMT ones.
With the double stuff, I was worried that it would be fragile in the pack, but the leather sheath seems to protect it well. You'll probably like it for a pack stone.