LE,
That Arx routine worked!. I started a new drawing, drew some text objects, loaded the Arx, and ran the code snippet you posted: (verticaltextstyle "standard")
The routine modify the "Standard" TextStyle to have vertical text. Cool! As Jeff mentioned, the drawing need to be Regen'd to update the existing text objects.
I wish I had more time to play with that C+ stuff, put darn work gets in the way...
Thanks for the Arx file! We run 2007 at work. I tested on 2006 at home.