I have an automatic tranny, and switched to Mobil 1 ATF in the tranny last year. I switched to Mobil 1 ATF in the transfer case earlier this year, and have had no problems at all.
The transfer case can use Dexron-III/Mercon compatible ATF or GL-4 oil, the rule of thumb seems to be use ATF if you have an automatic, and GL-4 if you have a manual. In other words, same type as in the tranny for the t-case.
For the front diff, I have Mobil 1 75W90 for over a year, no prob.
Brent