UPDATE 2
Just a note of caution...
Discovered that the new Vista plugin is calling G91 when the step mode is activated. However, it does not revert back to G90 (or G92) after the step jogging is complete. Switching to velocity mode also does not change it back. Only way I've found to get back to G90 is to enter it in MDI.
This may cause some unintended motion if an MDI command to move an axis is entered before manually programming G90. Also could be a serious issue if someone loads a program that is missing the G90 from the "safe" block at the beginning.
I've sent them an email asking them to see if there's a fix.
-Spumco