I'm rather seceptical about the auto tranny blowing if you use the over drive switch quite often, however I do have to say that about 6 months after I started using it on the Maxima that I had, the tranny fucked up as well. It was a 2000 Maxima with 65,000 on her at the time.

Replaced the tranny, never used the switch and it still drives with more than 100,000 on her. Who knows?