I finally got the Royal Purple in this weekend. The temp was about 8 degrees F. There was immediate improvement in shifting.
I had it done by a local mechanic because it was just too damn cold to do it myself. My dealership supposedly changed the fluid 10,000 miles ago (at 30,000 miles) with Mobil 80W90 GL5. The local guy said that it didn't look as though the drain plug had ever been removed - no wrench marks on it, and the fluid that drained looked too dark to be only 10,000 miles old.
So I don't know whether to be happy that maybe the dealer didn't change it at all (putting the wrong stuff in) or pissed that they charged me for changing it when they didn't.