Has anyone converted over to full synthetic automatic tranny fluid? If so, how's it working? What did you go with? How much did it cost?

We use our 2008 4Runner (V8 AWD) mainly for towing our camper (~4800#); it just turned over 40,000 miles and I am wanting to service the tranny. I've already converted over to full synthetic motor oil, differential fluid and transfer case oil.

Your experiences?