A week ago I tried topping off with a synthetic blend but immediately felt something different with the transmission bands, so I flushed it out and replaced it with regular oil the next day everything went back to normal.
Just sharing an observation. I'm not sure what material my bands are made with, but they look like they are probably cotton.
Beloe is a link to the forum discussion I found on the topic from 2012. I'm guessing that's the newest discussion unless there are new developments I did not find searching with Google.
The highlights seem to be that the "SF" designation on the oilcan indicates better resistance against Engine where than "SN" found on most modern oils.
Some people reported "chatter" with cotton bands, but someone with wooden bands said that synthetic was no problem. Many people commented that it is easier to start their engines in very cold weather when they use synthetic oil.
It all comes down to what your preference is. I run a high quality full synthetic high zinc 10W-40 in my car. BUT...I don't drive a lot of miles in a season, my car leaks very little. If I drove more miles or had a "gusher", I'd be using a cheaper brand for sure.